#include <bits/stdc++.h>

using namespace std;

int a[500000];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  freopen("tgc.inp", "r", stdin);

  int n;
  cin >> n;
  for (int i = 0; i < n; i++)
    cin >> a[i];
  sort(a, a + n);

  int res = 0;
  for (int i = 0; i < n - 1; i++) {
    if (a[i] != a[i + 1])
      continue;

    int l = i, r = n - 1;
    int mid;
    while (l < r) {
      mid = (l + r) / 2;

      if (a[mid] < 2 * a[i]) {
        l = mid + 1;
      } else {
        r = mid;
      }
    }
    res += r - mid + l;
  }
  cout << res << "\n";
}