#include <atcoder/all>
#include <bits/stdc++.h>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
using namespace atcoder;
using namespace std;

typedef long long ll;

void solve() {
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    sort(a.begin(), a.end());
    ll ans = 0;
    map<int, int> ma;
    rep(i, 0, n) ma[a[i]]++;
    int cnt = 0;
    a.emplace_back(2e9 + 10);
    for (auto [k, v] : ma) {
        while (a[cnt] < k * 2) {
            cnt++;
        }
        ans += (ll)(cnt - v) * v * (v - 1) / 2;
    }
    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    while (t--) {
        solve();
    }
}