#include <bits/stdc++.h>
using namespace std;

const int Dim = 900;

int N,T[Dim],Sol;

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

     scanf("%d",&N);

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

     sort(T + 1,T + N + 1);

    for (int i = 1;i < N;i++)
        for (int j = i + 1;j <= N;j++)
        {
            int Sum = T[j] + T[i],Y = upper_bound(T + i + 1,T + N + 1,Sum) - T - 1;

            Y -= j;

            Sol += Y;
        }

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

  return 0;
}