#include <bits/stdc++.h>

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n;
  std::cin >> n;
  std::vector<int> A(n);
  std::map<int, int> Mp;
  std::map<int, bool> vis;
  for (int i = 0; i < n; i++) {
    std::cin >> A[i];
    Mp[A[i]]++;
    vis[A[i]] = false;
  }
  std::sort(A.begin(), A.end());
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    if (Mp[A[i]] == 1) {
      continue;
    }
    if (vis[A[i]]) {
      continue;
    }
    vis[A[i]] = true;
    int cnt = std::lower_bound(A.begin(), A.end(), 2 * A[i]) - A.begin();
    ans += 1LL * (cnt - Mp[A[i]]) * Mp[A[i]] * (Mp[A[i]] - 1) / 2;
  }
  std::cout << ans << '\n';
}