#include <cstdio>
using namespace std;

const int Nmax = 801;

int main() {
    int n, x, i, j, k;
    int v[Nmax];

    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);

    scanf("%d", &n);
    for (i = 1; i <= n; ++i) {
        scanf("%d", &x);
        for (j = i-1; x < v[j] && j > 0; --j) {
            v[j+1] = v[j];
        }
        v[j+1] = x;
    }

    for (x = 0, i = 1; i <= n-2; ++i) {
        for (j = i+1; j <= n-1; ++j) {
            for (k = j+1; k <= n; ++k) {
                if (v[i]+v[j] >= v[k])
                    x++;
                else
                    k = n+1;
            }
        }
    }

    printf("%d\n", x);

    return 0;
}