#include <cstdio>
#define N 801
using namespace std;
int v[N];
int main()
{
    int n, nrtriangle = 0;
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    scanf("%d", &n);
    for(int i =  1; i<=n; i++)
        scanf("%d", &v[i]);
    for(int i = 1; i<n - 1; i++)
        for(int j = i  + 1; j<n; j++)
            for(int k =  j + 1; k <=n; k++)
    {
       int triangle = 1;
       if(v[i] + v[j] < v[k])
        triangle = 0;
       if(v[i] + v[k] < v[j])
        triangle = 0;
       if(v[j] + v[k] < v[i])
        triangle = 0;
       if(triangle)
        nrtriangle ++;
    }
    printf("%d", nrtriangle);
    return 0;
}