#include <fstream>
#include <cstdio>
#include <algorithm>

using namespace std;

int n,i,j,k,x,v[2005];

int main()
{
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    scanf("%d", &n);
    for (i=1; i<=n; i++)
      scanf("%d", &v[i]);
    sort(v+1, v+n+1);
    for (i=1; i<=n-2; i++)
    {
        for (j=i+1; j<=n-1; j++)
        {
            for (k=j+1; k<=n; k++)
            {
                if (v[i]+v[j]>=v[k])
                  x++;
                else
                  break;
            }
        }
    }
    printf("%d", x);
    return 0;
}