#include <bits/stdc++.h>

using namespace std;

int x[888];

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

    int n;
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i)
        scanf("%d", &x[i]);

    sort(x + 1, x + n + 1);
    int res = 0;
    for (int i = 1; i <= n; ++i) {
        int ptr = 0;
        for (int j = i + 1; j <= n; ++j) {
            if (ptr < j)
                ptr = j;
            while (ptr + 1 <= n && x[ptr + 1] <= x[i] + x[j])
                ++ptr;
            res += ptr - j;
        }
    }

    printf("%d", res);
    return 0;
}