#include <bits/stdc++.h>
#include <algorithm>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)
#define all(x) begin(x), end(x)

template <typename T> bool chmin(T& x, T y) {
	return x > y ? (x = y, true) : false;
}
template <typename T> bool chmax(T& x, T y) {
	return x < y ? (x = y, true) : false;
}

struct IOST {
	IOST() {
		ios::sync_with_stdio(false);
		cin.tie(nullptr);
		cout << fixed << setprecision(20);
	}
} IOST;

void solve() {
	int n;
	cin >> n;
	vector<int> a(n);
	rep(i, 0, n) cin >> a[i];
	map<int, ll> mp, smp;
	rep(i, 0, n) mp[a[i]]++;
	{
		ll tmp = 0;
		for (auto [x, y] : mp) {
			tmp += y;
			smp[x] = tmp;
		}
	}
	ll ans = 0;
	for (auto [x, y] : mp) {
		ll tmp = y * (y - 1) / 2;
		auto itr = smp.lower_bound(x * 2);
		itr--;
		tmp *= itr->second - y;
		ans += tmp;
	}
	cout << ans << "\n";
}

int main() {
	int t = 1;
	// cin >> t;
	rep(i, 0, t) solve();
}