#include <cstdio>
#include <algorithm>
using namespace std;
int v[805];
int main(){
    freopen("ntri.in", "r", stdin);
    freopen("ntri.out", "w", stdout);
    int n, i, i1, i2, i3, k = 0;
    scanf("%d", &n);
    for (i = 1; i <= n; i ++)
        scanf("%d", &v[i]);
    sort(v + 1, v + n + 1);
    for (i1 = 1; i1 <= n - 2; i1 ++)
        for (i2 = i1 + 1; i2 <= n - 1; i2 ++)
            for (i3 = i2 + 1; i3 <= n && v[i1] + v[i2] >= v[i3]; i3 ++)
                    k ++;
    printf("%d\n", k);
    return 0;
}