#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    ifstream cin("nrtri.in");
    ofstream cout("nrtri.out");

    int n;
    cin >> n;
    vector<int> v(n);
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
    }
    sort(v.begin(), v.end());

    int p, q, val, ans = 0;
    for (int i = 0; i < n - 2; ++i) {
        for (int j = i + 1; j < n - 1; ++j) {
            p = v[i]; q = v[j];
            val = p + q;

            int k = j + 1;
            while (val >= v[k] && k < n) {
                k++;
                ans++;
            }
        }
    }

    cout << ans;

    return 0;
}