#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
const int INF = 1000001000;
const long long INFLL = INF * 1LL * INF;
const int mod = 1000 * 1000 * 1000 + 7;
const int mod9 = 1000 * 1000 * 1000 + 9;
const int modr = 99990001;
const long double PI = 3.1415926535897932385;
template <class T>
void zero(T val, T& first) {
  first = val;
}
template <class T, class... Targs>
void zero(T val, T& first, Targs&... Fargs) {
  first = val;
  zero(val, Fargs...);
}
template <class T, class T2>
std::istream& operator>>(std::istream& is, pair<T, T2>& p) {
  return is >> p.first >> p.second;
}
template <class T>
std::istream& readN(T& first, int n, int st = 0) {
  for (int i = st, iend = (st + n - 1); i <= iend; i++) cin >> first[i];
  return cin;
}
template <class T>
std::istream& readS(set<T>& first, int n) {
  T second = *first.rbegin();
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    cin >> second;
    first.insert(second);
  }
  return cin;
}
template <class T>
std::istream& read(T& first) {
  return cin >> first;
}
template <class T, class... Targs>
std::istream& read(T& first, Targs&... Fargs) {
  return read(first), read(Fargs...);
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, pair<T, T2> p) {
  return os << p.first << " " << p.second;
}
template <class T>
std::ostream& operator<<(std::ostream& os, vector<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, set<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, multiset<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, map<T, T2> v) {
  bool f = true;
  for (pair<T, T2> second : v) {
    if (!f) os << ' ';
    os << second.first << "=>" << second.second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& outV(T first, char del = ' ') {
  bool f = true;
  for (auto second : first) {
    if (!f) cout << del;
    cout << second;
    f = false;
  }
  return cout;
}
template <class T>
std::ostream& outN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n == -1 ? (int)first.size() - 1 : st + n - 1);
       i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outAN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n - 1); i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outA2(T first, int n, int m) {
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    for (int j = 0, jend = (m - 1); j <= jend; j++)
      cout << first[i][j] << (j == m - 1 ? '\n' : ' ');
  }
  return cout;
}
template <class T>
std::ostream& out(T first) {
  return cout << first;
}
template <class T, class... Targs>
std::ostream& out(T first, Targs... Fargs) {
  return out(first) << " ", out(Fargs...);
}
template <typename T>
void srt(T& a, int st, int fn, bool isArr) {
  sort(a + st, a + fn + 1);
}
template <class T>
void srt(T& a, int st = 0, int fn = 0) {
  sort(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
template <typename T>
T rev_num(T a) {
  T r = 0;
  for (; a; a /= 10) r = r * 10 + a % 10;
  return r;
}
template <typename T>
void rev(T& a, int st, int fn, bool isArr) {
  reverse(a + st, a + fn + 1);
}
template <class T>
void rev(T& a, int st = 0, int fn = 0) {
  reverse(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
long long sqr(long long a) { return a * a; };
long long sqr(int a) { return a * 1LL * a; };
long double sqr(long double a) { return a * a; };
long long phi(int n) {
  int res = n;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) {
      while (n % i == 0) n /= i;
      res -= res / i;
    }
  if (n > 1) res -= res / n;
  return res;
}
long long bpm(long long a, long long n = -2, long long m = mod) {
  n = n < 0 ? n + m : n;
  long long r = 1;
  while (n) {
    if (n & 1) r = (r * a) % m;
    a = (a * a) % m;
    n >>= 1;
  }
  return r;
}
unsigned long long gcd(unsigned long long a, unsigned long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
vector<int> ero_p, ero_l;
void ero(int n) {
  ero_l.resize(n + 1);
  ero_l[0] = -1;
  for (int i = 2, iend = (n); i <= iend; i++)
    if (!ero_l[i]) {
      ero_p.push_back(i);
      ero_l[i] = i;
      for (long long j = i * 1LL * i; j <= n; j += i) {
        ero_l[j] = i;
      }
    }
}
long long gcd_cb(long long a, long long b, long long& first,
                 long long& second) {
  if (!b) {
    first = 1;
    second = 0;
    return a;
  }
  long long x1, y1, g;
  g = gcd_cb(b, a % b, x1, y1);
  first = y1;
  second = x1 - a / b * y1;
  return g;
}
vector<long long> fact;
void fact_prec(int n = 20) {
  fact.resize(n + 1);
  fact[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    fact[i] = fact[i - 1] * i;
  }
}
vector<long double> factd;
void fact_precd(int n = 146) {
  factd.resize(n + 1);
  factd[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    factd[i] = factd[i - 1] * i;
  }
}
string str(long long a) {
  string r = "";
  for (; a; a /= 10) r += a % 10 + '0';
  rev(r);
  return r;
}
const int N = 400005;
int c[N], a[N];
int l[N], r[N];
int t[N];
void incT(int l, int r, int c, int v = 1) {
  int md = (l + r) >> 1;
  int lv = v << 1;
  int rv = lv + 1;
  if (l == r) {
    t[v]++;
    return;
  }
  if (c <= md) {
    incT(l, md, c, lv);
  } else {
    incT(md + 1, r, c, rv);
  }
  t[v]++;
}
int getT(int l, int r, int ask_l, int ask_r, int v = 1) {
  if (l == ask_l && r == ask_r) {
    return t[v];
  }
  int md = (l + r) >> 1;
  int lv = v << 1;
  int rv = lv + 1;
  if (ask_r <= md) {
    return getT(l, md, ask_l, ask_r, lv);
  } else if (ask_l > md) {
    return getT(md + 1, r, ask_l, ask_r, rv);
  } else {
    return getT(l, md, ask_l, md, lv) + getT(md + 1, r, md + 1, ask_r, rv);
  }
}
void solution() {
  int n;
  read(n);
  readN(a, 2 * n);
  for (int i = 0, iend = (2 * n - 1); i <= iend; i++) {
    int first = a[i];
    c[first]++;
    if (c[first] == 2) {
      r[first] = i;
    } else {
      l[first] = i;
    }
  }
  int res = 0;
  for (int i = 0, iend = (2 * n - 1); i <= iend; i++) {
    int first = a[i];
    c[first]--;
    if (c[first]) {
      incT(0, 2 * n, r[first]);
      res += (r[first] - l[first] - getT(0, 2 * n, l[first], r[first]));
    }
  }
  out(res) << "\n";
}
int main() {
  ios::sync_with_stdio(false);
  solution();
  return 0;
}

### Prompt

Construct a CPP code solution to the problem outlined:

Allen is hosting a formal dinner party. 2n people come to the event in n pairs (couples). After a night of fun, Allen wants to line everyone up for a final picture. The 2n people line up, but Allen doesn't like the ordering. Allen prefers if each pair occupies adjacent positions in the line, as this makes the picture more aesthetic.

Help Allen find the minimum number of swaps of adjacent positions he must perform to make it so that each couple occupies adjacent positions in the line.

Input

The first line contains a single integer n (1 ≤ n ≤ 100), the number of pairs of people.

The second line contains 2n integers a_1, a_2, ..., a_{2n}. For each i with 1 ≤ i ≤ n, i appears exactly twice. If a_j = a_k = i, that means that the j-th and k-th people in the line form a couple.

Output

Output a single integer, representing the minimum number of adjacent swaps needed to line the people up so that each pair occupies adjacent positions.

Examples

Input

4
1 1 2 3 3 2 4 4


Output

2


Input

3
1 1 2 2 3 3


Output

0


Input

3
3 1 2 3 1 2


Output

3

Note

In the first sample case, we can transform 1 1 2 3 3 2 4 4 → 1 1 2 3 2 3 4 4 → 1 1 2 2 3 3 4 4 in two steps. Note that the sequence 1 1 2 3 3 2 4 4 → 1 1 3 2 3 2 4 4 → 1 1 3 3 2 2 4 4 also works in the same number of steps.

The second sample case already satisfies the constraints; therefore we need 0 swaps.

### Response

```cpp
#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
const int INF = 1000001000;
const long long INFLL = INF * 1LL * INF;
const int mod = 1000 * 1000 * 1000 + 7;
const int mod9 = 1000 * 1000 * 1000 + 9;
const int modr = 99990001;
const long double PI = 3.1415926535897932385;
template <class T>
void zero(T val, T& first) {
  first = val;
}
template <class T, class... Targs>
void zero(T val, T& first, Targs&... Fargs) {
  first = val;
  zero(val, Fargs...);
}
template <class T, class T2>
std::istream& operator>>(std::istream& is, pair<T, T2>& p) {
  return is >> p.first >> p.second;
}
template <class T>
std::istream& readN(T& first, int n, int st = 0) {
  for (int i = st, iend = (st + n - 1); i <= iend; i++) cin >> first[i];
  return cin;
}
template <class T>
std::istream& readS(set<T>& first, int n) {
  T second = *first.rbegin();
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    cin >> second;
    first.insert(second);
  }
  return cin;
}
template <class T>
std::istream& read(T& first) {
  return cin >> first;
}
template <class T, class... Targs>
std::istream& read(T& first, Targs&... Fargs) {
  return read(first), read(Fargs...);
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, pair<T, T2> p) {
  return os << p.first << " " << p.second;
}
template <class T>
std::ostream& operator<<(std::ostream& os, vector<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, set<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& operator<<(std::ostream& os, multiset<T> v) {
  bool f = true;
  for (auto second : v) {
    if (!f) os << ' ';
    os << second;
    f = false;
  }
  return os;
}
template <class T, class T2>
std::ostream& operator<<(std::ostream& os, map<T, T2> v) {
  bool f = true;
  for (pair<T, T2> second : v) {
    if (!f) os << ' ';
    os << second.first << "=>" << second.second;
    f = false;
  }
  return os;
}
template <class T>
std::ostream& outV(T first, char del = ' ') {
  bool f = true;
  for (auto second : first) {
    if (!f) cout << del;
    cout << second;
    f = false;
  }
  return cout;
}
template <class T>
std::ostream& outN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n == -1 ? (int)first.size() - 1 : st + n - 1);
       i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outAN(T first, int n = -1, int st = 0) {
  for (int i = st, iend = (n - 1); i <= iend; i++) {
    cout << first[i];
    if (i < iend) cout << ' ';
  }
  return cout;
}
template <class T>
std::ostream& outA2(T first, int n, int m) {
  for (int i = 0, iend = (n - 1); i <= iend; i++) {
    for (int j = 0, jend = (m - 1); j <= jend; j++)
      cout << first[i][j] << (j == m - 1 ? '\n' : ' ');
  }
  return cout;
}
template <class T>
std::ostream& out(T first) {
  return cout << first;
}
template <class T, class... Targs>
std::ostream& out(T first, Targs... Fargs) {
  return out(first) << " ", out(Fargs...);
}
template <typename T>
void srt(T& a, int st, int fn, bool isArr) {
  sort(a + st, a + fn + 1);
}
template <class T>
void srt(T& a, int st = 0, int fn = 0) {
  sort(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
template <typename T>
T rev_num(T a) {
  T r = 0;
  for (; a; a /= 10) r = r * 10 + a % 10;
  return r;
}
template <typename T>
void rev(T& a, int st, int fn, bool isArr) {
  reverse(a + st, a + fn + 1);
}
template <class T>
void rev(T& a, int st = 0, int fn = 0) {
  reverse(a.begin() + st, fn ? a.begin() + fn + 1 : a.end());
}
long long sqr(long long a) { return a * a; };
long long sqr(int a) { return a * 1LL * a; };
long double sqr(long double a) { return a * a; };
long long phi(int n) {
  int res = n;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) {
      while (n % i == 0) n /= i;
      res -= res / i;
    }
  if (n > 1) res -= res / n;
  return res;
}
long long bpm(long long a, long long n = -2, long long m = mod) {
  n = n < 0 ? n + m : n;
  long long r = 1;
  while (n) {
    if (n & 1) r = (r * a) % m;
    a = (a * a) % m;
    n >>= 1;
  }
  return r;
}
unsigned long long gcd(unsigned long long a, unsigned long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
vector<int> ero_p, ero_l;
void ero(int n) {
  ero_l.resize(n + 1);
  ero_l[0] = -1;
  for (int i = 2, iend = (n); i <= iend; i++)
    if (!ero_l[i]) {
      ero_p.push_back(i);
      ero_l[i] = i;
      for (long long j = i * 1LL * i; j <= n; j += i) {
        ero_l[j] = i;
      }
    }
}
long long gcd_cb(long long a, long long b, long long& first,
                 long long& second) {
  if (!b) {
    first = 1;
    second = 0;
    return a;
  }
  long long x1, y1, g;
  g = gcd_cb(b, a % b, x1, y1);
  first = y1;
  second = x1 - a / b * y1;
  return g;
}
vector<long long> fact;
void fact_prec(int n = 20) {
  fact.resize(n + 1);
  fact[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    fact[i] = fact[i - 1] * i;
  }
}
vector<long double> factd;
void fact_precd(int n = 146) {
  factd.resize(n + 1);
  factd[0] = 1;
  for (int i = 1, iend = (n); i <= iend; i++) {
    factd[i] = factd[i - 1] * i;
  }
}
string str(long long a) {
  string r = "";
  for (; a; a /= 10) r += a % 10 + '0';
  rev(r);
  return r;
}
const int N = 400005;
int c[N], a[N];
int l[N], r[N];
int t[N];
void incT(int l, int r, int c, int v = 1) {
  int md = (l + r) >> 1;
  int lv = v << 1;
  int rv = lv + 1;
  if (l == r) {
    t[v]++;
    return;
  }
  if (c <= md) {
    incT(l, md, c, lv);
  } else {
    incT(md + 1, r, c, rv);
  }
  t[v]++;
}
int getT(int l, int r, int ask_l, int ask_r, int v = 1) {
  if (l == ask_l && r == ask_r) {
    return t[v];
  }
  int md = (l + r) >> 1;
  int lv = v << 1;
  int rv = lv + 1;
  if (ask_r <= md) {
    return getT(l, md, ask_l, ask_r, lv);
  } else if (ask_l > md) {
    return getT(md + 1, r, ask_l, ask_r, rv);
  } else {
    return getT(l, md, ask_l, md, lv) + getT(md + 1, r, md + 1, ask_r, rv);
  }
}
void solution() {
  int n;
  read(n);
  readN(a, 2 * n);
  for (int i = 0, iend = (2 * n - 1); i <= iend; i++) {
    int first = a[i];
    c[first]++;
    if (c[first] == 2) {
      r[first] = i;
    } else {
      l[first] = i;
    }
  }
  int res = 0;
  for (int i = 0, iend = (2 * n - 1); i <= iend; i++) {
    int first = a[i];
    c[first]--;
    if (c[first]) {
      incT(0, 2 * n, r[first]);
      res += (r[first] - l[first] - getT(0, 2 * n, l[first], r[first]));
    }
  }
  out(res) << "\n";
}
int main() {
  ios::sync_with_stdio(false);
  solution();
  return 0;
}

```