#include <iostream>
#include <fstream>

using namespace std;

ifstream f ("nrtri.in");
ofstream g ("nrtri.out");

int n, cnt;

int main()
{
    f >> n;
    int a[n+1];
    for (int i = 1; i <= n; i ++)
        f >> a[i];
    for (int i = 1; i < n; i ++)
        for (int j = i+1; j <= n; j ++)
            if (a[i] > a[j])
            {
                int aux = a[i];
                a[i] = a[j];
                a[j] = aux;
            }
    for (int i = 1; i <= n-2; i ++)
        for (int j = i+1; j <= n-1; j ++)
            for (int k = j+1; k <= n; k ++)
                if (a[i] + a[j] >= a[k])
                    cnt ++;
    g << cnt;
    return 0;
}