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

const int NMAX = 805, SMAX = 60005;

int N, V[NMAX], S[SMAX], Ans;

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

    scanf("%i", &N);
    for(int i = 1; i <= N; ++ i)
    {
        scanf("%i", &V[i]);
        for(int j = 1; j < i; ++ j)
            S[V[i] + V[j]] ++;
    }

    for(int i = 1; i < SMAX; ++ i)
        S[i] += S[i - 1];

    Ans = (N * (N - 1) * (N - 2)) / 6;
    for(int i = 1; i <= N; ++ i)
        Ans -= S[ V[i] - 1 ];

    printf("%i\n", Ans);

    return 0;
}