#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
std::istream &operator>>(std::istream &i, pair<T, U> &p) {
  i >> p.first >> p.second;
  return i;
}
template <typename T>
std::istream &operator>>(std::istream &i, vector<T> &t) {
  for (auto &v : t) {
    i >> v;
  }
  return i;
}
template <typename T>
std::ostream &operator<<(std::ostream &o, const vector<T> &t) {
  for (size_t i = 0; i < t.size(); ++i) {
    o << t[i] << " \n"[i == t.size() - 1];
  }
  return o;
}
template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;
template <typename T>
using maxheap = priority_queue<T, vector<T>, less<T>>;
auto fraclt = [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
  return (long long)a.first * b.second < (long long)b.first * a.second;
};
struct cmpfrac {
  bool operator()(const std::pair<int, int> &a,
                  const std::pair<int, int> &b) const {
    return (long long)a.first * b.second < (long long)b.first * a.second;
  }
};
template <typename T>
bool in(T a, T b, T c) {
  return a <= b && b < c;
}
unsigned int logceil(long long first) {
  unsigned int b = 0;
  while (first) {
    first >>= 1;
    ++b;
  }
  return b;
}
namespace std {
template <typename T, typename U>
struct hash<pair<T, U>> {
  hash<T> t;
  hash<U> u;
  size_t operator()(const pair<T, U> &p) const {
    return t(p.first) ^ (u(p.second) << 7);
  }
};
}  // namespace std
template <typename T, typename F>
T bsh(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      l = m + 1;
      r = m;
    } else {
      h = m - 1;
    }
  }
  return r;
}
template <typename F>
double bsh(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      l = m;
    } else {
      h = m;
    }
  }
  return (l + h) / 2;
}
template <typename T, typename F>
T bsl(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      h = m - 1;
      r = m;
    } else {
      l = m + 1;
    }
  }
  return r;
}
template <typename F>
double bsl(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      h = m;
    } else {
      l = m;
    }
  }
  return (l + h) / 2;
}
template <typename T>
T gcd(T a, T b) {
  if (a < b) swap(a, b);
  return b ? gcd(b, a % b) : a;
}
template <typename T>
class vector2 : public vector<vector<T>> {
 public:
  vector2() {}
  vector2(size_t a, size_t b, T t = T())
      : vector<vector<T>>(a, vector<T>(b, t)) {}
};
template <typename T>
class vector3 : public vector<vector<vector<T>>> {
 public:
  vector3() {}
  vector3(size_t a, size_t b, size_t c, T t = T())
      : vector<vector<vector<T>>>(a, vector<vector<T>>(b, vector<T>(c, t))) {}
};
template <typename T>
struct bounded_priority_queue {
  inline bounded_priority_queue(unsigned int X) : A(X), B(0) {}
  inline void push(unsigned int L, T V) {
    B = max(B, L);
    A[L].push(V);
  }
  inline const T &top() const { return A[B].front(); }
  inline void pop() {
    A[B].pop();
    while (B > 0 && A[B].empty()) --B;
  }
  inline bool empty() const { return A[B].empty(); }
  inline void clear() {
    B = 0;
    for (auto &a : A) a = queue<T>();
  }

 private:
  vector<queue<T>> A;
  unsigned int B;
};
struct UnionFind {
  UnionFind(size_t N) : P(N, -1), comp(N) {}
  int find(int first) {
    while (P[first] >= 0) {
      first = P[first];
    }
    return first;
  }
  bool united(int first, int second) { return find(first) == find(second); }
  bool unite(int first, int second) {
    first = find(first);
    second = find(second);
    if (first == second) {
      return false;
    }
    --comp;
    if (P[first] > P[second]) {
      swap(first, second);
    }
    P[first] += P[second];
    P[second] = first;
    return true;
  }
  vector<int> P;
  size_t comp;
};
unsigned long long mulull(unsigned long long a, unsigned long long z,
                          unsigned long long mod) {
  __int128 result = ((__int128)a * (__int128)z) % (__int128)mod;
  return (unsigned long long)result;
}
pair<unsigned long long, unsigned long long> mulull(unsigned long long a,
                                                    unsigned long long b) {
  __int128 result = (__int128)a * (__int128)b;
  return {(unsigned long long)(result >> 64), (unsigned long long)result};
}
bool fractionGreaterOrEqual(long long a, long long b, long long c,
                            long long d) {
  if (b < 0) {
    b = -b;
    a = -a;
  }
  if (d < 0) {
    d = -d;
    c = -c;
  }
  return a < 0 && c < 0 ? mulull(-a, d) <= mulull(-c, b)
                        : (a >= 0) && (c < 0 || mulull(a, d) >= mulull(c, b));
}
bool fractionGreaterOrEqual(double a, double b, double c, double d) {
  return a / b >= c / d;
}
namespace Envelope {
template <typename T>
struct Line {
  T m, b;
  mutable function<const Line<T> *()> succ;
  bool operator<(const Line &rhs) const {
    if (rhs.b != numeric_limits<T>::min()) return m < rhs.m;
    const Line *s = succ();
    if (!s) return 0;
    return b - s->b < (s->m - m) * rhs.m;
  }
};
template <typename T>
struct Upper : public multiset<Envelope::Line<T>> {
  using parent = multiset<Line<T>>;
  bool bad(typename parent::iterator second) {
    auto z = next(second);
    if (second == parent::begin()) {
      return z != parent::end() && second->m == z->m && second->b <= z->b;
    } else {
      auto first = prev(second);
      if (z == parent::end()) {
        return second->m == first->m && second->b <= first->b;
      } else {
        return fractionGreaterOrEqual(first->b - second->b,
                                      second->m - first->m, second->b - z->b,
                                      z->m - second->m);
      }
    }
  }
  void insert_line(T m, T b) {
    auto second = parent::insert({m, b});
    second->succ = [=] {
      return next(second) == parent::end() ? 0 : &*next(second);
    };
    if (bad(second)) {
      parent::erase(second);
      return;
    }
    while (next(second) != parent::end() && bad(next(second)))
      parent::erase(next(second));
    while (second != parent::begin() && bad(prev(second)))
      parent::erase(prev(second));
  }
  T operator[](T first) const {
    auto l = parent::lower_bound({first, numeric_limits<T>::min()});
    return l == parent::end() ? numeric_limits<T>::min() : l->m * first + l->b;
  }
};
template <typename T>
struct Lower : public Upper<T> {
  void insert_line(T m, T b) { Upper<T>::insert_line(-m, -b); }
  T operator[](T first) const { return -Upper<T>::operator[](first); }
};
}  // namespace Envelope
struct Sieve : public std::vector<bool> {
  explicit Sieve(unsigned int n) : vector<bool>(n + 1, true), n(n) {
    at(0) = false;
    at(1) = false;
    for (unsigned int i = 2; i * i <= n; ++i) {
      if (at(i))
        for (int j = i * i; j <= n; j += i) (*this)[j] = false;
    }
  }
  vector<int> primes() const {
    vector<int> ans;
    for (int i = 2; i <= n; ++i)
      if (at(i)) ans.push_back(i);
    return ans;
  }

 private:
  int n;
};
struct Moebius : public std::vector<std::pair<int, int>> {
  explicit Moebius(unsigned int n) : Moebius(n, Sieve{n}.primes()) {}
  Moebius(unsigned int n, const vector<int> &primes) {
    search(-1, 1, 1, n, primes);
    std::sort(begin(), end());
  }

 private:
  void search(int i, int first, int second, int n, const vector<int> &primes) {
    push_back({first, second});
    while (++i < primes.size() && (long long)first * primes[i] <= n)
      search(i, first * primes[i], -second, n, primes);
  }
};
struct LargePrimes : public vector<int> {
  LargePrimes()
      : vector<int>{
            7,     9,     21,    33,    87,    93,    97,    103,   123,
            181,   207,   223,   241,   271,   289,   297,   321,   349,
            363,   403,   409,   411,   427,   433,   439,   447,   453,
            459,   483,   513,   531,   579,   607,   613,   637,   663,
            711,   753,   787,   801,   829,   861,   871,   891,   901,
            919,   931,   933,   993,   1011,  1021,  1053,  1087,  1099,
            1137,  1161,  1203,  1213,  1237,  1263,  1269,  1273,  1279,
            1311,  1329,  1333,  1351,  1371,  1393,  1413,  1447,  1449,
            1491,  1501,  1531,  1537,  1539,  1581,  1617,  1621,  1633,
            1647,  1663,  1677,  1699,  1759,  1773,  1789,  1791,  1801,
            1803,  1819,  1857,  1887,  1917,  1927,  1957,  1963,  1969,
            2043,  2089,  2103,  2139,  2149,  2161,  2173,  2187,  2193,
            2233,  2239,  2277,  2307,  2359,  2361,  2431,  2449,  2457,
            2499,  2571,  2581,  2607,  2631,  2637,  2649,  2667,  2727,
            2791,  2803,  2821,  2823,  2827,  2907,  2937,  2989,  3009,
            3013,  3051,  3057,  3097,  3111,  3133,  3153,  3157,  3163,
            3211,  3241,  3247,  3253,  3267,  3271,  3273,  3283,  3309,
            3337,  3351,  3357,  3373,  3379,  3397,  3469,  3471,  3513,
            3519,  3559,  3577,  3579,  3601,  3621,  3643,  3651,  3663,
            3679,  3709,  3747,  3751,  3769,  3777,  3787,  3793,  3843,
            3853,  3871,  3889,  3891,  3909,  3919,  3931,  3951,  3957,
            3967,  3987,  3999,  4023,  4059,  4099,  4119,  4123,  4207,
            4233,  4249,  4251,  4263,  4321,  4329,  4381,  4389,  4437,
            4449,  4459,  4497,  4507,  4519,  4539,  4567,  4569,  4581,
            4609,  4611,  4627,  4633,  4647,  4693,  4699,  4717,  4771,
            4777,  4783,  4791,  4807,  4839,  4843,  4849,  4857,  4867,
            4869,  4891,  4893,  4897,  4927,  4933,  4977,  4981,  5001,
            5029,  5053,  5067,  5103,  5133,  5187,  5197,  5203,  5233,
            5277,  5287,  5299,  5317,  5329,  5341,  5353,  5361,  5403,
            5407,  5437,  5443,  5449,  5451,  5469,  5491,  5527,  5541,
            5547,  5583,  5631,  5647,  5683,  5731,  5737,  5751,  5763,
            5791,  5823,  5827,  5833,  5847,  5863,  5899,  5907,  5947,
            5953,  5959,  5971,  5973,  5991,  5997,  6019,  6027,  6037,
            6039,  6061,  6093,  6099,  6127,  6129,  6177,  6193,  6211,
            6223,  6229,  6307,  6313,  6331,  6349,  6379,  6393,  6417,
            6421,  6457,  6459,  6477,  6541,  6571,  6577,  6583,  6607,
            6621,  6661,  6663,  6697,  6717,  6751,  6781,  6837,  6867,
            6901,  6957,  6961,  6967,  6981,  7003,  7023,  7027,  7089,
            7117,  7137,  7147,  7159,  7191,  7209,  7237,  7243,  7257,
            7279,  7321,  7347,  7383,  7389,  7417,  7429,  7447,  7453,
            7467,  7479,  7497,  7513,  7521,  7531,  7537,  7557,  7633,
            7647,  7651,  7653,  7681,  7707,  7719,  7741,  7759,  7773,
            7803,  7819,  7837,  7873,  7887,  7909,  7923,  7927,  7929,
            7941,  8041,  8083,  8089,  8101,  8109,  8127,  8173,  8181,
            8223,  8257,  8259,  8271,  8277,  8311,  8313,  8343,  8349,
            8397,  8403,  8419,  8431,  8439,  8487,  8511,  8557,  8593,
            8617,  8637,  8649,  8661,  8671,  8679,  8719,  8727,  8761,
            8773,  8791,  8797,  8803,  8811,  8829,  8853,  8899,  8917,
            8937,  8967,  9009,  9013,  9063,  9081,  9093,  9099,  9123,
            9133,  9163,  9183,  9211,  9223,  9259,  9277,  9279,  9289,
            9301,  9321,  9331,  9363,  9399,  9403,  9421,  9441,  9457,
            9469,  9487,  9519,  9529,  9531,  9541,  9559,  9561,  9567,
            9573,  9579,  9597,  9601,  9609,  9631,  9651,  9667,  9679,
            9711,  9733,  9739,  9757,  9789,  9831,  9859,  9867,  9961,
            9999,  10029, 10051, 10069, 10101, 10153, 10173, 10189, 10197,
            10233, 10243, 10251, 10267, 10281, 10303, 10321, 10327, 10351,
            10357, 10381, 10449, 10467, 10483, 10503, 10513, 10549, 10593,
            10597, 10611, 10633, 10659, 10699, 10707, 10723, 10747, 10749,
            10761, 10773, 10777, 10801, 10833, 10903, 10953, 10969, 10971,
            10981, 10987, 11007, 11011, 11071, 11083, 11091, 11107, 11109,
            11137, 11149, 11161, 11223, 11239, 11253, 11269, 11277, 11283,
            11289, 11301, 11317, 11329, 11371, 11377, 11391, 11421, 11479,
            11487, 11497, 11517, 11533, 11539, 11559, 11583, 11601, 11619,
            11631, 11659, 11673, 11679, 11707, 11763, 11767, 11769, 11773,
            11799, 11811, 11821, 11823, 11847, 11869, 11967, 11983, 11989,
            12019, 12037, 12121, 12157, 12177, 12187, 12217, 12219, 12231,
            12241, 12253, 12297, 12309, 12333, 12337, 12339, 12361, 12367,
            12399, 12411, 12459, 12463, 12483, 12501, 12513, 12523, 12547,
            12553, 12577, 12609, 12631, 12649, 12679, 12681, 12703, 12723,
            12733, 12747, 12753, 12759, 12799, 12847, 12877, 12891, 12901,
            12903, 12927, 12939, 12963, 13011, 13017, 13029, 13039, 13081,
            13087, 13089, 13101, 13107, 13137, 13141, 13143, 13153, 13191,
            13207, 13213, 13237, 13323, 13369, 13419, 13437, 13447, 13477,
            13519, 13537, 13561, 13563, 13587, 13591, 13723, 13741, 13759,
            13789, 13801, 13857, 13881, 13897, 13921, 13923, 13939, 13999,
            14011, 14073, 14077, 14083, 14097, 14121, 14131, 14143, 14157,
            14161, 14167, 14181, 14193, 14209, 14241, 14259, 14271, 14293,
            14361, 14391, 14397, 14437, 14529, 14551, 14581, 14583, 14599,
            14607, 14611, 14643, 14727, 14761, 14773, 14779, 14791, 14823,
            14853, 14881, 14889, 14901, 14931, 14937, 14997, 15031, 15043,
            15057, 15063, 15069, 15097, 15103, 15109, 15117, 15141, 15147,
            15187, 15199, 15217, 15231, 15253, 15271, 15279, 15283, 15307,
            15339, 15349, 15351, 15363, 15369, 15409, 15427, 15447, 15477,
            15487, 15553, 15579, 15591, 15649, 15651, 15673, 15693, 15703,
            15717, 15727, 15747, 15799, 15811, 15823, 15859, 15889, 15963,
            15981, 16009, 16021, 16029, 16047, 16063, 16089, 16093, 16107,
            16153, 16167, 16191, 16201, 16231, 16233, 16261, 16267, 16273,
            16317, 16323, 16411, 16419, 16431, 16489, 16491, 16513, 16539,
            16617, 16621, 16623, 16627, 16651, 16659, 16671, 16711} {
    for (int &i : *this) i += 1000000000;
  }
};
bool isPrime(long long n) {
  for (int p :
       {2,   3,   5,   7,   11,  13,  17,  19,  23,  29,  31,  37,  41,  43,
        47,  53,  59,  61,  67,  71,  73,  79,  83,  89,  97,  101, 103, 107,
        109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181,
        191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257})
    if (p < n && n % p == 0) return false;
  long long d = n - 1, r = 0;
  while (d % 2 == 0) {
    d /= 2;
    r += 1;
  }
  auto composite = [=](int a) {
    long long first = 1, p = a, e = d;
    while (e > 0) {
      if (e % 2 > 0) {
        first = mulull(first, p, n);
      }
      e /= 2;
      p = mulull(p, p, n);
    }
    if (first == 1 || first == n - 1) return false;
    for (int i = 1; i < r; ++i) {
      first = mulull(first, first, n);
      if (first == 1) return true;
      if (first == n - 1) return false;
    }
    return true;
  };
  return !(composite(2)) && (n < 2047 || !composite(3)) &&
         (n < 1373653 || !composite(5)) && (n < 25326001 || !composite(7)) &&
         (n < 3215031751LL || !composite(11)) &&
         (n < 2152302898747LL || !composite(13)) &&
         (n < 3474749660383LL || !composite(17)) &&
         (n < 341550071728321LL || (!composite(19) && !composite(23))) &&
         (n < 3825123056546413051LL ||
          (!composite(29) && !composite(31) && !composite(37)));
}
class TaskD {
 public:
  void solve(istream &cin, ostream &cout) {
    unsigned int N;
    cin >> N;
    Sieve S{N};
    auto P = S.primes();
    Moebius M{N, P};
    long long pairs1 = 0;
    for (auto &m : M) {
      if (m.first == 1) continue;
      pairs1 -= m.second * (long long)(N / m.first) *
                (long long)(N / m.first - 1) / 2;
    }
    vector<int> Z(N + 1, 0);
    for (int i = 2; i * i <= N; ++i) {
      if (!Z[i]) {
        Z[i] = i;
        for (int j = i * i; j <= N; j += i) {
          if (!Z[j]) Z[j] = i;
        }
      }
    }
    for (int i = 2; i <= N; ++i)
      if (!Z[i]) Z[i] = i;
    vector<int> C(N + 1, 0);
    for (int i = 0; i <= N; ++i) {
      C[Z[i]]++;
    }
    vector<int> D = C;
    for (int i = N - 1; i >= 0; --i) {
      D[i] += D[i + 1];
    }
    long long pairs3 = 0;
    int badPrimes = D[N / 2 + 1];
    for (unsigned int i = 3; i < N; ++i) {
      if (C[i]) {
        int q = max(i, N / i) + 1;
        if (q > 2) {
          pairs3 += (long long)C[i] * max(0, D[q] - badPrimes);
        }
      }
    }
    int valid = N - 1 - badPrimes;
    cout << (long long)valid * (valid - 1) - pairs1 + pairs3 << endl;
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  TaskD solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}

### Prompt

Your task is to create a Cpp solution to the following problem:

You are given a positive integer n. Let's build a graph on vertices 1, 2, ..., n in such a way that there is an edge between vertices u and v if and only if <image>. Let d(u, v) be the shortest distance between u and v, or 0 if there is no path between them. Compute the sum of values d(u, v) over all 1 ≤ u < v ≤ n.

The gcd (greatest common divisor) of two positive integers is the maximum positive integer that divides both of the integers.

Input

Single integer n (1 ≤ n ≤ 107).

Output

Print the sum of d(u, v) over all 1 ≤ u < v ≤ n.

Examples

Input

6


Output

8


Input

10


Output

44

Note

All shortest paths in the first example: 

  * <image>
  * <image>
  * <image>
  * <image>
  * <image>
  * <image>



There are no paths between other pairs of vertices.

The total distance is 2 + 1 + 1 + 2 + 1 + 1 = 8.

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
std::istream &operator>>(std::istream &i, pair<T, U> &p) {
  i >> p.first >> p.second;
  return i;
}
template <typename T>
std::istream &operator>>(std::istream &i, vector<T> &t) {
  for (auto &v : t) {
    i >> v;
  }
  return i;
}
template <typename T>
std::ostream &operator<<(std::ostream &o, const vector<T> &t) {
  for (size_t i = 0; i < t.size(); ++i) {
    o << t[i] << " \n"[i == t.size() - 1];
  }
  return o;
}
template <typename T>
using minheap = priority_queue<T, vector<T>, greater<T>>;
template <typename T>
using maxheap = priority_queue<T, vector<T>, less<T>>;
auto fraclt = [](const std::pair<int, int> &a, const std::pair<int, int> &b) {
  return (long long)a.first * b.second < (long long)b.first * a.second;
};
struct cmpfrac {
  bool operator()(const std::pair<int, int> &a,
                  const std::pair<int, int> &b) const {
    return (long long)a.first * b.second < (long long)b.first * a.second;
  }
};
template <typename T>
bool in(T a, T b, T c) {
  return a <= b && b < c;
}
unsigned int logceil(long long first) {
  unsigned int b = 0;
  while (first) {
    first >>= 1;
    ++b;
  }
  return b;
}
namespace std {
template <typename T, typename U>
struct hash<pair<T, U>> {
  hash<T> t;
  hash<U> u;
  size_t operator()(const pair<T, U> &p) const {
    return t(p.first) ^ (u(p.second) << 7);
  }
};
}  // namespace std
template <typename T, typename F>
T bsh(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      l = m + 1;
      r = m;
    } else {
      h = m - 1;
    }
  }
  return r;
}
template <typename F>
double bsh(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      l = m;
    } else {
      h = m;
    }
  }
  return (l + h) / 2;
}
template <typename T, typename F>
T bsl(T l, T h, const F &f) {
  T r = -1, m;
  while (l <= h) {
    m = (l + h) / 2;
    if (f(m)) {
      h = m - 1;
      r = m;
    } else {
      l = m + 1;
    }
  }
  return r;
}
template <typename F>
double bsl(double l, double h, const F &f, double p = 1e-9) {
  unsigned int r = 3 + (unsigned int)log2((h - l) / p);
  while (r--) {
    double m = (l + h) / 2;
    if (f(m)) {
      h = m;
    } else {
      l = m;
    }
  }
  return (l + h) / 2;
}
template <typename T>
T gcd(T a, T b) {
  if (a < b) swap(a, b);
  return b ? gcd(b, a % b) : a;
}
template <typename T>
class vector2 : public vector<vector<T>> {
 public:
  vector2() {}
  vector2(size_t a, size_t b, T t = T())
      : vector<vector<T>>(a, vector<T>(b, t)) {}
};
template <typename T>
class vector3 : public vector<vector<vector<T>>> {
 public:
  vector3() {}
  vector3(size_t a, size_t b, size_t c, T t = T())
      : vector<vector<vector<T>>>(a, vector<vector<T>>(b, vector<T>(c, t))) {}
};
template <typename T>
struct bounded_priority_queue {
  inline bounded_priority_queue(unsigned int X) : A(X), B(0) {}
  inline void push(unsigned int L, T V) {
    B = max(B, L);
    A[L].push(V);
  }
  inline const T &top() const { return A[B].front(); }
  inline void pop() {
    A[B].pop();
    while (B > 0 && A[B].empty()) --B;
  }
  inline bool empty() const { return A[B].empty(); }
  inline void clear() {
    B = 0;
    for (auto &a : A) a = queue<T>();
  }

 private:
  vector<queue<T>> A;
  unsigned int B;
};
struct UnionFind {
  UnionFind(size_t N) : P(N, -1), comp(N) {}
  int find(int first) {
    while (P[first] >= 0) {
      first = P[first];
    }
    return first;
  }
  bool united(int first, int second) { return find(first) == find(second); }
  bool unite(int first, int second) {
    first = find(first);
    second = find(second);
    if (first == second) {
      return false;
    }
    --comp;
    if (P[first] > P[second]) {
      swap(first, second);
    }
    P[first] += P[second];
    P[second] = first;
    return true;
  }
  vector<int> P;
  size_t comp;
};
unsigned long long mulull(unsigned long long a, unsigned long long z,
                          unsigned long long mod) {
  __int128 result = ((__int128)a * (__int128)z) % (__int128)mod;
  return (unsigned long long)result;
}
pair<unsigned long long, unsigned long long> mulull(unsigned long long a,
                                                    unsigned long long b) {
  __int128 result = (__int128)a * (__int128)b;
  return {(unsigned long long)(result >> 64), (unsigned long long)result};
}
bool fractionGreaterOrEqual(long long a, long long b, long long c,
                            long long d) {
  if (b < 0) {
    b = -b;
    a = -a;
  }
  if (d < 0) {
    d = -d;
    c = -c;
  }
  return a < 0 && c < 0 ? mulull(-a, d) <= mulull(-c, b)
                        : (a >= 0) && (c < 0 || mulull(a, d) >= mulull(c, b));
}
bool fractionGreaterOrEqual(double a, double b, double c, double d) {
  return a / b >= c / d;
}
namespace Envelope {
template <typename T>
struct Line {
  T m, b;
  mutable function<const Line<T> *()> succ;
  bool operator<(const Line &rhs) const {
    if (rhs.b != numeric_limits<T>::min()) return m < rhs.m;
    const Line *s = succ();
    if (!s) return 0;
    return b - s->b < (s->m - m) * rhs.m;
  }
};
template <typename T>
struct Upper : public multiset<Envelope::Line<T>> {
  using parent = multiset<Line<T>>;
  bool bad(typename parent::iterator second) {
    auto z = next(second);
    if (second == parent::begin()) {
      return z != parent::end() && second->m == z->m && second->b <= z->b;
    } else {
      auto first = prev(second);
      if (z == parent::end()) {
        return second->m == first->m && second->b <= first->b;
      } else {
        return fractionGreaterOrEqual(first->b - second->b,
                                      second->m - first->m, second->b - z->b,
                                      z->m - second->m);
      }
    }
  }
  void insert_line(T m, T b) {
    auto second = parent::insert({m, b});
    second->succ = [=] {
      return next(second) == parent::end() ? 0 : &*next(second);
    };
    if (bad(second)) {
      parent::erase(second);
      return;
    }
    while (next(second) != parent::end() && bad(next(second)))
      parent::erase(next(second));
    while (second != parent::begin() && bad(prev(second)))
      parent::erase(prev(second));
  }
  T operator[](T first) const {
    auto l = parent::lower_bound({first, numeric_limits<T>::min()});
    return l == parent::end() ? numeric_limits<T>::min() : l->m * first + l->b;
  }
};
template <typename T>
struct Lower : public Upper<T> {
  void insert_line(T m, T b) { Upper<T>::insert_line(-m, -b); }
  T operator[](T first) const { return -Upper<T>::operator[](first); }
};
}  // namespace Envelope
struct Sieve : public std::vector<bool> {
  explicit Sieve(unsigned int n) : vector<bool>(n + 1, true), n(n) {
    at(0) = false;
    at(1) = false;
    for (unsigned int i = 2; i * i <= n; ++i) {
      if (at(i))
        for (int j = i * i; j <= n; j += i) (*this)[j] = false;
    }
  }
  vector<int> primes() const {
    vector<int> ans;
    for (int i = 2; i <= n; ++i)
      if (at(i)) ans.push_back(i);
    return ans;
  }

 private:
  int n;
};
struct Moebius : public std::vector<std::pair<int, int>> {
  explicit Moebius(unsigned int n) : Moebius(n, Sieve{n}.primes()) {}
  Moebius(unsigned int n, const vector<int> &primes) {
    search(-1, 1, 1, n, primes);
    std::sort(begin(), end());
  }

 private:
  void search(int i, int first, int second, int n, const vector<int> &primes) {
    push_back({first, second});
    while (++i < primes.size() && (long long)first * primes[i] <= n)
      search(i, first * primes[i], -second, n, primes);
  }
};
struct LargePrimes : public vector<int> {
  LargePrimes()
      : vector<int>{
            7,     9,     21,    33,    87,    93,    97,    103,   123,
            181,   207,   223,   241,   271,   289,   297,   321,   349,
            363,   403,   409,   411,   427,   433,   439,   447,   453,
            459,   483,   513,   531,   579,   607,   613,   637,   663,
            711,   753,   787,   801,   829,   861,   871,   891,   901,
            919,   931,   933,   993,   1011,  1021,  1053,  1087,  1099,
            1137,  1161,  1203,  1213,  1237,  1263,  1269,  1273,  1279,
            1311,  1329,  1333,  1351,  1371,  1393,  1413,  1447,  1449,
            1491,  1501,  1531,  1537,  1539,  1581,  1617,  1621,  1633,
            1647,  1663,  1677,  1699,  1759,  1773,  1789,  1791,  1801,
            1803,  1819,  1857,  1887,  1917,  1927,  1957,  1963,  1969,
            2043,  2089,  2103,  2139,  2149,  2161,  2173,  2187,  2193,
            2233,  2239,  2277,  2307,  2359,  2361,  2431,  2449,  2457,
            2499,  2571,  2581,  2607,  2631,  2637,  2649,  2667,  2727,
            2791,  2803,  2821,  2823,  2827,  2907,  2937,  2989,  3009,
            3013,  3051,  3057,  3097,  3111,  3133,  3153,  3157,  3163,
            3211,  3241,  3247,  3253,  3267,  3271,  3273,  3283,  3309,
            3337,  3351,  3357,  3373,  3379,  3397,  3469,  3471,  3513,
            3519,  3559,  3577,  3579,  3601,  3621,  3643,  3651,  3663,
            3679,  3709,  3747,  3751,  3769,  3777,  3787,  3793,  3843,
            3853,  3871,  3889,  3891,  3909,  3919,  3931,  3951,  3957,
            3967,  3987,  3999,  4023,  4059,  4099,  4119,  4123,  4207,
            4233,  4249,  4251,  4263,  4321,  4329,  4381,  4389,  4437,
            4449,  4459,  4497,  4507,  4519,  4539,  4567,  4569,  4581,
            4609,  4611,  4627,  4633,  4647,  4693,  4699,  4717,  4771,
            4777,  4783,  4791,  4807,  4839,  4843,  4849,  4857,  4867,
            4869,  4891,  4893,  4897,  4927,  4933,  4977,  4981,  5001,
            5029,  5053,  5067,  5103,  5133,  5187,  5197,  5203,  5233,
            5277,  5287,  5299,  5317,  5329,  5341,  5353,  5361,  5403,
            5407,  5437,  5443,  5449,  5451,  5469,  5491,  5527,  5541,
            5547,  5583,  5631,  5647,  5683,  5731,  5737,  5751,  5763,
            5791,  5823,  5827,  5833,  5847,  5863,  5899,  5907,  5947,
            5953,  5959,  5971,  5973,  5991,  5997,  6019,  6027,  6037,
            6039,  6061,  6093,  6099,  6127,  6129,  6177,  6193,  6211,
            6223,  6229,  6307,  6313,  6331,  6349,  6379,  6393,  6417,
            6421,  6457,  6459,  6477,  6541,  6571,  6577,  6583,  6607,
            6621,  6661,  6663,  6697,  6717,  6751,  6781,  6837,  6867,
            6901,  6957,  6961,  6967,  6981,  7003,  7023,  7027,  7089,
            7117,  7137,  7147,  7159,  7191,  7209,  7237,  7243,  7257,
            7279,  7321,  7347,  7383,  7389,  7417,  7429,  7447,  7453,
            7467,  7479,  7497,  7513,  7521,  7531,  7537,  7557,  7633,
            7647,  7651,  7653,  7681,  7707,  7719,  7741,  7759,  7773,
            7803,  7819,  7837,  7873,  7887,  7909,  7923,  7927,  7929,
            7941,  8041,  8083,  8089,  8101,  8109,  8127,  8173,  8181,
            8223,  8257,  8259,  8271,  8277,  8311,  8313,  8343,  8349,
            8397,  8403,  8419,  8431,  8439,  8487,  8511,  8557,  8593,
            8617,  8637,  8649,  8661,  8671,  8679,  8719,  8727,  8761,
            8773,  8791,  8797,  8803,  8811,  8829,  8853,  8899,  8917,
            8937,  8967,  9009,  9013,  9063,  9081,  9093,  9099,  9123,
            9133,  9163,  9183,  9211,  9223,  9259,  9277,  9279,  9289,
            9301,  9321,  9331,  9363,  9399,  9403,  9421,  9441,  9457,
            9469,  9487,  9519,  9529,  9531,  9541,  9559,  9561,  9567,
            9573,  9579,  9597,  9601,  9609,  9631,  9651,  9667,  9679,
            9711,  9733,  9739,  9757,  9789,  9831,  9859,  9867,  9961,
            9999,  10029, 10051, 10069, 10101, 10153, 10173, 10189, 10197,
            10233, 10243, 10251, 10267, 10281, 10303, 10321, 10327, 10351,
            10357, 10381, 10449, 10467, 10483, 10503, 10513, 10549, 10593,
            10597, 10611, 10633, 10659, 10699, 10707, 10723, 10747, 10749,
            10761, 10773, 10777, 10801, 10833, 10903, 10953, 10969, 10971,
            10981, 10987, 11007, 11011, 11071, 11083, 11091, 11107, 11109,
            11137, 11149, 11161, 11223, 11239, 11253, 11269, 11277, 11283,
            11289, 11301, 11317, 11329, 11371, 11377, 11391, 11421, 11479,
            11487, 11497, 11517, 11533, 11539, 11559, 11583, 11601, 11619,
            11631, 11659, 11673, 11679, 11707, 11763, 11767, 11769, 11773,
            11799, 11811, 11821, 11823, 11847, 11869, 11967, 11983, 11989,
            12019, 12037, 12121, 12157, 12177, 12187, 12217, 12219, 12231,
            12241, 12253, 12297, 12309, 12333, 12337, 12339, 12361, 12367,
            12399, 12411, 12459, 12463, 12483, 12501, 12513, 12523, 12547,
            12553, 12577, 12609, 12631, 12649, 12679, 12681, 12703, 12723,
            12733, 12747, 12753, 12759, 12799, 12847, 12877, 12891, 12901,
            12903, 12927, 12939, 12963, 13011, 13017, 13029, 13039, 13081,
            13087, 13089, 13101, 13107, 13137, 13141, 13143, 13153, 13191,
            13207, 13213, 13237, 13323, 13369, 13419, 13437, 13447, 13477,
            13519, 13537, 13561, 13563, 13587, 13591, 13723, 13741, 13759,
            13789, 13801, 13857, 13881, 13897, 13921, 13923, 13939, 13999,
            14011, 14073, 14077, 14083, 14097, 14121, 14131, 14143, 14157,
            14161, 14167, 14181, 14193, 14209, 14241, 14259, 14271, 14293,
            14361, 14391, 14397, 14437, 14529, 14551, 14581, 14583, 14599,
            14607, 14611, 14643, 14727, 14761, 14773, 14779, 14791, 14823,
            14853, 14881, 14889, 14901, 14931, 14937, 14997, 15031, 15043,
            15057, 15063, 15069, 15097, 15103, 15109, 15117, 15141, 15147,
            15187, 15199, 15217, 15231, 15253, 15271, 15279, 15283, 15307,
            15339, 15349, 15351, 15363, 15369, 15409, 15427, 15447, 15477,
            15487, 15553, 15579, 15591, 15649, 15651, 15673, 15693, 15703,
            15717, 15727, 15747, 15799, 15811, 15823, 15859, 15889, 15963,
            15981, 16009, 16021, 16029, 16047, 16063, 16089, 16093, 16107,
            16153, 16167, 16191, 16201, 16231, 16233, 16261, 16267, 16273,
            16317, 16323, 16411, 16419, 16431, 16489, 16491, 16513, 16539,
            16617, 16621, 16623, 16627, 16651, 16659, 16671, 16711} {
    for (int &i : *this) i += 1000000000;
  }
};
bool isPrime(long long n) {
  for (int p :
       {2,   3,   5,   7,   11,  13,  17,  19,  23,  29,  31,  37,  41,  43,
        47,  53,  59,  61,  67,  71,  73,  79,  83,  89,  97,  101, 103, 107,
        109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181,
        191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257})
    if (p < n && n % p == 0) return false;
  long long d = n - 1, r = 0;
  while (d % 2 == 0) {
    d /= 2;
    r += 1;
  }
  auto composite = [=](int a) {
    long long first = 1, p = a, e = d;
    while (e > 0) {
      if (e % 2 > 0) {
        first = mulull(first, p, n);
      }
      e /= 2;
      p = mulull(p, p, n);
    }
    if (first == 1 || first == n - 1) return false;
    for (int i = 1; i < r; ++i) {
      first = mulull(first, first, n);
      if (first == 1) return true;
      if (first == n - 1) return false;
    }
    return true;
  };
  return !(composite(2)) && (n < 2047 || !composite(3)) &&
         (n < 1373653 || !composite(5)) && (n < 25326001 || !composite(7)) &&
         (n < 3215031751LL || !composite(11)) &&
         (n < 2152302898747LL || !composite(13)) &&
         (n < 3474749660383LL || !composite(17)) &&
         (n < 341550071728321LL || (!composite(19) && !composite(23))) &&
         (n < 3825123056546413051LL ||
          (!composite(29) && !composite(31) && !composite(37)));
}
class TaskD {
 public:
  void solve(istream &cin, ostream &cout) {
    unsigned int N;
    cin >> N;
    Sieve S{N};
    auto P = S.primes();
    Moebius M{N, P};
    long long pairs1 = 0;
    for (auto &m : M) {
      if (m.first == 1) continue;
      pairs1 -= m.second * (long long)(N / m.first) *
                (long long)(N / m.first - 1) / 2;
    }
    vector<int> Z(N + 1, 0);
    for (int i = 2; i * i <= N; ++i) {
      if (!Z[i]) {
        Z[i] = i;
        for (int j = i * i; j <= N; j += i) {
          if (!Z[j]) Z[j] = i;
        }
      }
    }
    for (int i = 2; i <= N; ++i)
      if (!Z[i]) Z[i] = i;
    vector<int> C(N + 1, 0);
    for (int i = 0; i <= N; ++i) {
      C[Z[i]]++;
    }
    vector<int> D = C;
    for (int i = N - 1; i >= 0; --i) {
      D[i] += D[i + 1];
    }
    long long pairs3 = 0;
    int badPrimes = D[N / 2 + 1];
    for (unsigned int i = 3; i < N; ++i) {
      if (C[i]) {
        int q = max(i, N / i) + 1;
        if (q > 2) {
          pairs3 += (long long)C[i] * max(0, D[q] - badPrimes);
        }
      }
    }
    int valid = N - 1 - badPrimes;
    cout << (long long)valid * (valid - 1) - pairs1 + pairs3 << endl;
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  TaskD solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}

```