# include <iostream>
# include <fstream>
# include <algorithm>
using namespace std;

# define MOD 66013
# define MAXN 810

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

int a[MAXN];

int main()
{
    int sol = 0, n;
    f >> n;
    for (int i = 1; i <= n; i++) {
        f >> a[i];
    }

    sort(a + 1, a + n + 1);

    for (int i = 1; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
            for (int l = j + 1; l <= n; l++) {
                if (a[i] + a[j] >= a[l]) {
                    sol++;
                } else {
                    l = n + 1;
                }
            }
        }
    }
    g << sol;

    return 0;
}