#include <bits/stdc++.h>
using namespace std;
int n, i, j, k, nr = 0;
int l[805];
int main(){
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    scanf("%d", &n);
    for (i = 1; i <= n; i ++)
        scanf("%d", &l[i]);
    sort(l + 1, l + n + 1);
    for (i = 1; i <= n - 2; i ++)
        for (j = i + 1; j <= n - 1; j ++)
            for (k = j + 1; k <= n && l[i] + l[j] >= l[k]; k ++)
                    nr ++;
    printf("%d\n", nr);
    return 0;
}