#include <bits/stdc++.h>

using namespace std;

ifstream fin ("medie.in");
ofstream fout ("medie.out");

const int VALMAX = 7000;
int f[VALMAX + 2];
int main() {
  int n, i, j, x, ans;
  fin >> n;

  for (i = 1; i <= n; ++i) {
    fin >> x;
    ++f[x];
  }

  ans = 0;
  for (i = 1; i <= VALMAX; ++i) {
    for (j = i; j >= 1; j -= 2) {
      int mid = (i + j) >> 1;
      if (i == j) {
        ans = ans + f[i] * (f[i] - 1) * (f[i] - 2) / 2;
        continue;
      }
      ans = ans + f[mid] * f[i] * f[j];
    }
  }
  fout << ans;
  return 0;
}