#include <bits/stdc++.h>
using namespace std;

#define rep(i, l, r) for (int i = (int)(l); i<(int)(r); i++)
#define ll long long

int main() {
    int N; cin >> N;
    vector<int> A(N);
    rep(i, 0, N) cin >> A[i];
    sort(A.begin(), A.end());
    map<int, int> cnt;
    rep(i, 0, N) {
        cnt[A[i]]++;
    }
    ll ans = 0;
    for (auto[key, val] : cnt) {
        ll t = lower_bound(A.begin(), A.end(), 2*key) - A.begin();
        t -= val;
        ans += t * val * (val-1)/2;
    }
    cout << ans << endl;
}