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

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int main()
{
    int v[1000];
    int n;
    fin >> n;
    for (int i = 1; i <= n; i++)
        fin >> v[i];
    int cate_triunghiuri = 0;

    for (int i = 1; i <= n; i++)
    {
        for (int j = i + 1; j<= n; j++)
        {
            for (int k = j + 1; k<= n; k++)
            {
                if (v[i] + v[j] >= v[k] and 
                v[i] + v[k] >= v[j] and v[j] + v[k] >= v[i])
                    cate_triunghiuri++;
            }
        }
    }

    fout << cate_triunghiuri;
    return 0;
}