#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

void solve() {
  ll n;
  cin >> n;
  vector<ll> a(n);
  map<ll, ll> mp;
  rep(i, n) cin >> a[i], mp[a[i]]++;
  sort(a.begin(), a.end());
  ll ans = 0;
  for (const auto &[k, v] : mp) {
    if (v >= 2) {
      ll c = lower_bound(a.begin(), a.end(), k * 2) - a.begin() - v;
      ans += c * v * (v - 1) / 2;
    }
  }
  cout << ans << '\n';
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  int T = 1;
  for (int t = 0; t < T; t++) {
    solve();
  }
  return 0;
}