#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif

int main()
{
    int64_t n;
    cin >> n;
    vector<int64_t> as(n);
    for (auto &&a : as)
    {
        cin >> a;
    }

    ranges::sort(as);

    map<int64_t, int64_t> mp;
    for (auto &&a : as)
    {
        mp[a]++;
    }

    int64_t ans = 0;

    for (auto [k, v] : mp)
    {
        if (2 <= v)
        {
            auto itr = ranges::lower_bound(as, 2 * k);
            int64_t t = distance(as.begin(), itr);
            t -= v;

            ans += v * (v - 1) / 2 * t;
        }
    }

    cout << ans << endl;

    return 0;
}