#include <fstream>

using namespace std;
int v[800];
int main()
{
    ifstream cin ("nrtri.in");
    ofstream cout ("nrtri.out");
    int n, nr = 0;
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        cin >> v[i];
    }
    for (int i = 0; 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] && v[i] + v[k] >= v[j] && v[j] + v[k] >= v[i])
                {
                    nr++;
                }
            }
        }
    }
    cout << nr;
    return 0;
}