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;
int main() {
  long long n;
  cin >> n;
  vector<long long> a(n);
  long long i;
  for (i = 0; i < n; i++) cin >> a[i];
  map<long long, long long> m;
  long long add = 0;
  for (i = 0; i < n; i++) {
    auto it = m.find(a[i]);
    if (it != m.end()) {
      pair<long long, long long> p = *it;
      long long val = p.second;
      m.erase(a[i]);
      m.insert(make_pair(a[i], val + 1));
    } else {
      m.insert(make_pair(a[i], 1));
    }
    auto itneg = m.find(a[i] - 1);
    auto itpos = m.find(a[i] + 1);
    if (itneg != m.end()) {
      pair<long long, long long> p = *itneg;
      add -= p.second;
    }
    if (itpos != m.end()) {
      pair<long long, long long> p = *itpos;
      add += p.second;
    }
  }
  long long ans = add;
  long long ch = 0;
  for (i = 0; i < n; i++) {
    ans += a[i] * (i * 2 - (n - 1));
    while (ans >= 1000000000000000000) {
      ch++;
      ans -= 1000000000000000000;
    }
    while (ans < 0) {
      ch--;
      ans += 1000000000000000000;
    }
  }
  if (ch >= 0) {
    if (ch == 0)
      cout << ans << endl;
    else {
      cout << ch;
      vector<int> nums(18);
      for (i = 17; i >= 0; i--) {
        nums[i] = ans % 10;
        ans /= 10;
      }
      for (i = 0; i < 18; i++) {
        cout << nums[i];
      }
      cout << endl;
    }
  } else {
    ch++;
    ans -= 1000000000000000000;
    if (ch == 0) {
      cout << ans << endl;
    } else {
      ans = abs(ans);
      cout << '-';
      if (ch < 0) cout << abs(ch);
      vector<int> nums(18);
      for (i = 17; i >= 0; i--) {
        nums[i] = ans % 10;
        ans /= 10;
      }
      for (i = 0; i < 18; i++) {
        cout << nums[i];
      }
      cout << endl;
    }
  }
}
