Let's denote a function 

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You are given an array a consisting of n integers. You have to calculate the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Input

The first line contains one integer n (1 ≤ n ≤ 200000) — the number of elements in a.

The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 109) — elements of the array. 

Output

Print one integer — the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Examples

Input

5
1 2 3 1 3


Output

4


Input

4
6 6 5 5


Output

0


Input

4
6 6 4 4


Output

-8

Note

In the first example:

  1. d(a1, a2) = 0; 
  2. d(a1, a3) = 2; 
  3. d(a1, a4) = 0; 
  4. d(a1, a5) = 2; 
  5. d(a2, a3) = 0; 
  6. d(a2, a4) = 0; 
  7. d(a2, a5) = 0; 
  8. d(a3, a4) = - 2; 
  9. d(a3, a5) = 0; 
  10. d(a4, a5) = 2. 
#include <bits/stdc++.h>
using namespace std;
using namespace std;
const int base = 1000000000;
const int base_digits = 9;
struct bigint {
  vector<int> z;
  int sign;
  bigint() : sign(1) {}
  bigint(long long v) { *this = v; }
  bigint(const string &s) { read(s); }
  void operator=(const bigint &v) {
    sign = v.sign;
    z = v.z;
  }
  void operator=(long long v) {
    sign = 1;
    if (v < 0) sign = -1, v = -v;
    z.clear();
    for (; v > 0; v = v / base) z.push_back(v % base);
  }
  bigint operator+(const bigint &v) const {
    if (sign == v.sign) {
      bigint res = v;
      for (int i = 0, carry = 0; i < (int)max(z.size(), v.z.size()) || carry;
           ++i) {
        if (i == (int)res.z.size()) res.z.push_back(0);
        res.z[i] += carry + (i < (int)z.size() ? z[i] : 0);
        carry = res.z[i] >= base;
        if (carry) res.z[i] -= base;
      }
      return res;
    }
    return *this - (-v);
  }
  bigint operator-(const bigint &v) const {
    if (sign == v.sign) {
      if (abs() >= v.abs()) {
        bigint res = *this;
        for (int i = 0, carry = 0; i < (int)v.z.size() || carry; ++i) {
          res.z[i] -= carry + (i < (int)v.z.size() ? v.z[i] : 0);
          carry = res.z[i] < 0;
          if (carry) res.z[i] += base;
        }
        res.trim();
        return res;
      }
      return -(v - *this);
    }
    return *this + (-v);
  }
  void operator*=(int v) {
    if (v < 0) sign = -sign, v = -v;
    for (int i = 0, carry = 0; i < (int)z.size() || carry; ++i) {
      if (i == (int)z.size()) z.push_back(0);
      long long cur = z[i] * (long long)v + carry;
      carry = (int)(cur / base);
      z[i] = (int)(cur % base);
    }
    trim();
  }
  bigint operator*(int v) const {
    bigint res = *this;
    res *= v;
    return res;
  }
  friend pair<bigint, bigint> divmod(const bigint &a1, const bigint &b1) {
    int norm = base / (b1.z.back() + 1);
    bigint a = a1.abs() * norm;
    bigint b = b1.abs() * norm;
    bigint q, r;
    q.z.resize(a.z.size());
    for (int i = a.z.size() - 1; i >= 0; i--) {
      r *= base;
      r += a.z[i];
      int s1 = b.z.size() < r.z.size() ? r.z[b.z.size()] : 0;
      int s2 = b.z.size() - 1 < r.z.size() ? r.z[b.z.size() - 1] : 0;
      int d = ((long long)s1 * base + s2) / b.z.back();
      r -= b * d;
      while (r < 0) r += b, --d;
      q.z[i] = d;
    }
    q.sign = a1.sign * b1.sign;
    r.sign = a1.sign;
    q.trim();
    r.trim();
    return make_pair(q, r / norm);
  }
  friend bigint sqrt(const bigint &a1) {
    bigint a = a1;
    while (a.z.empty() || a.z.size() % 2 == 1) a.z.push_back(0);
    int n = a.z.size();
    int firstDigit = (int)sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
    int norm = base / (firstDigit + 1);
    a *= norm;
    a *= norm;
    while (a.z.empty() || a.z.size() % 2 == 1) a.z.push_back(0);
    bigint r = (long long)a.z[n - 1] * base + a.z[n - 2];
    firstDigit = (int)sqrt((double)a.z[n - 1] * base + a.z[n - 2]);
    int q = firstDigit;
    bigint res;
    for (int j = n / 2 - 1; j >= 0; j--) {
      for (;; --q) {
        bigint r1 =
            (r - (res * 2 * base + q) * q) * base * base +
            (j > 0 ? (long long)a.z[2 * j - 1] * base + a.z[2 * j - 2] : 0);
        if (r1 >= 0) {
          r = r1;
          break;
        }
      }
      res *= base;
      res += q;
      if (j > 0) {
        int d1 = res.z.size() + 2 < r.z.size() ? r.z[res.z.size() + 2] : 0;
        int d2 = res.z.size() + 1 < r.z.size() ? r.z[res.z.size() + 1] : 0;
        int d3 = res.z.size() < r.z.size() ? r.z[res.z.size()] : 0;
        q = ((long long)d1 * base * base + (long long)d2 * base + d3) /
            (firstDigit * 2);
      }
    }
    res.trim();
    return res / norm;
  }
  bigint operator/(const bigint &v) const { return divmod(*this, v).first; }
  bigint operator%(const bigint &v) const { return divmod(*this, v).second; }
  void operator/=(int v) {
    if (v < 0) sign = -sign, v = -v;
    for (int i = (int)z.size() - 1, rem = 0; i >= 0; --i) {
      long long cur = z[i] + rem * (long long)base;
      z[i] = (int)(cur / v);
      rem = (int)(cur % v);
    }
    trim();
  }
  bigint operator/(int v) const {
    bigint res = *this;
    res /= v;
    return res;
  }
  int operator%(int v) const {
    if (v < 0) v = -v;
    int m = 0;
    for (int i = z.size() - 1; i >= 0; --i)
      m = (z[i] + m * (long long)base) % v;
    return m * sign;
  }
  void operator+=(const bigint &v) { *this = *this + v; }
  void operator-=(const bigint &v) { *this = *this - v; }
  void operator*=(const bigint &v) { *this = *this * v; }
  void operator/=(const bigint &v) { *this = *this / v; }
  bool operator<(const bigint &v) const {
    if (sign != v.sign) return sign < v.sign;
    if (z.size() != v.z.size()) return z.size() * sign < v.z.size() * v.sign;
    for (int i = z.size() - 1; i >= 0; i--)
      if (z[i] != v.z[i]) return z[i] * sign < v.z[i] * sign;
    return false;
  }
  bool operator>(const bigint &v) const { return v < *this; }
  bool operator<=(const bigint &v) const { return !(v < *this); }
  bool operator>=(const bigint &v) const { return !(*this < v); }
  bool operator==(const bigint &v) const {
    return !(*this < v) && !(v < *this);
  }
  bool operator!=(const bigint &v) const { return *this < v || v < *this; }
  void trim() {
    while (!z.empty() && z.back() == 0) z.pop_back();
    if (z.empty()) sign = 1;
  }
  bool isZero() const { return z.empty() || (z.size() == 1 && !z[0]); }
  bigint operator-() const {
    bigint res = *this;
    res.sign = -sign;
    return res;
  }
  bigint abs() const {
    bigint res = *this;
    res.sign *= res.sign;
    return res;
  }
  long long longValue() const {
    long long res = 0;
    for (int i = z.size() - 1; i >= 0; i--) res = res * base + z[i];
    return res * sign;
  }
  friend bigint gcd(const bigint &a, const bigint &b) {
    return b.isZero() ? a : gcd(b, a % b);
  }
  friend bigint lcm(const bigint &a, const bigint &b) {
    return a / gcd(a, b) * b;
  }
  void read(const string &s) {
    sign = 1;
    z.clear();
    int pos = 0;
    while (pos < (int)s.size() && (s[pos] == '-' || s[pos] == '+')) {
      if (s[pos] == '-') sign = -sign;
      ++pos;
    }
    for (int i = s.size() - 1; i >= pos; i -= base_digits) {
      int x = 0;
      for (int j = max(pos, i - base_digits + 1); j <= i; j++)
        x = x * 10 + s[j] - '0';
      z.push_back(x);
    }
    trim();
  }
  friend istream &operator>>(istream &stream, bigint &v) {
    string s;
    stream >> s;
    v.read(s);
    return stream;
  }
  friend ostream &operator<<(ostream &stream, const bigint &v) {
    if (v.sign == -1) stream << '-';
    stream << (v.z.empty() ? 0 : v.z.back());
    for (int i = (int)v.z.size() - 2; i >= 0; --i)
      stream << setw(base_digits) << setfill('0') << v.z[i];
    return stream;
  }
  static vector<int> convert_base(const vector<int> &a, int old_digits,
                                  int new_digits) {
    vector<long long> p(max(old_digits, new_digits) + 1);
    p[0] = 1;
    for (int i = 1; i < (int)p.size(); i++) p[i] = p[i - 1] * 10;
    vector<int> res;
    long long cur = 0;
    int cur_digits = 0;
    for (int i = 0; i < (int)a.size(); i++) {
      cur += a[i] * p[cur_digits];
      cur_digits += old_digits;
      while (cur_digits >= new_digits) {
        res.push_back(int(cur % p[new_digits]));
        cur /= p[new_digits];
        cur_digits -= new_digits;
      }
    }
    res.push_back((int)cur);
    while (!res.empty() && res.back() == 0) res.pop_back();
    return res;
  }
  static vector<long long> karatsubaMultiply(const vector<long long> &a,
                                             const vector<long long> &b) {
    int n = a.size();
    vector<long long> res(n + n);
    if (n <= 32) {
      for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++) res[i + j] += a[i] * b[j];
      return res;
    }
    int k = n >> 1;
    vector<long long> a1(a.begin(), a.begin() + k);
    vector<long long> a2(a.begin() + k, a.end());
    vector<long long> b1(b.begin(), b.begin() + k);
    vector<long long> b2(b.begin() + k, b.end());
    vector<long long> a1b1 = karatsubaMultiply(a1, b1);
    vector<long long> a2b2 = karatsubaMultiply(a2, b2);
    for (int i = 0; i < k; i++) a2[i] += a1[i];
    for (int i = 0; i < k; i++) b2[i] += b1[i];
    vector<long long> r = karatsubaMultiply(a2, b2);
    for (int i = 0; i < (int)a1b1.size(); i++) r[i] -= a1b1[i];
    for (int i = 0; i < (int)a2b2.size(); i++) r[i] -= a2b2[i];
    for (int i = 0; i < (int)r.size(); i++) res[i + k] += r[i];
    for (int i = 0; i < (int)a1b1.size(); i++) res[i] += a1b1[i];
    for (int i = 0; i < (int)a2b2.size(); i++) res[i + n] += a2b2[i];
    return res;
  }
  bigint operator*(const bigint &v) const {
    vector<int> a6 = convert_base(this->z, base_digits, 6);
    vector<int> b6 = convert_base(v.z, base_digits, 6);
    vector<long long> a(a6.begin(), a6.end());
    vector<long long> b(b6.begin(), b6.end());
    while (a.size() < b.size()) a.push_back(0);
    while (b.size() < a.size()) b.push_back(0);
    while (a.size() & (a.size() - 1)) a.push_back(0), b.push_back(0);
    vector<long long> c = karatsubaMultiply(a, b);
    bigint res;
    res.sign = sign * v.sign;
    for (int i = 0, carry = 0; i < (int)c.size(); i++) {
      long long cur = c[i] + carry;
      res.z.push_back((int)(cur % 1000000));
      carry = (int)(cur / 1000000);
    }
    res.z = convert_base(res.z, 6, base_digits);
    res.trim();
    return res;
  }
};
bigint random_bigint(int n) {
  string s;
  for (int i = 0; i < n; i++) {
    s += rand() % 10 + '0';
  }
  return bigint(s);
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  map<int, int> kie;
  int n;
  cin >> n;
  bigint sum = 0;
  bigint ats = 0;
  for (int i = 0; i < n; i++) {
    long long x;
    cin >> x;
    ats += bigint(x) * i - sum;
    ats -= kie[x - 1];
    ats += kie[x + 1];
    sum += x;
    kie[x]++;
  }
  cout << ats << "\n";
  return 0;
}
