#include <cstdio>
#include <algorithm>
using namespace std;

const int NMAX = 803;
int V[NMAX];

int main () {

    freopen ("nrtri.in", "r", stdin);
    freopen ("nrtri.out", "w", stdout);
    int N, i, j, k = 0;
    scanf ("%d", &N);
    for (i = 1; i <= N; ++i)
        scanf ("%d", &V[i]);
    sort (V + 1, V + N + 1);
    for (i = 1; i < N - 1; ++i)
        for (j = i + 1; j < N; ++j)
            k += upper_bound (V + j + 1, V + N + 1, V[i] + V[j]) - V - 1 - j;
    printf ("%d", k);

}