#include <iostream>
#include <vector>
#include <algorithm>
#include <map>

using namespace std;

int main()
{
    int n;
    cin >> n;
    map<int, int> mp;
    vector<int> a(n);
    for (int i = 0; i < n; ++i)
    {
        cin >> a[i];
        ++mp[a[i]];
    }
    sort(a.begin(), a.end());
    long long ans = 0;
    for (auto [k, c] : mp)
    {
        auto id = lower_bound(a.begin(), a.end(), 2 * k) - a.begin();
        ans += (long long)c * (c - 1) / 2 * (id - c);
    }
    cout << ans << endl;
}