#include <cstdio>
#include <algorithm>
using namespace std;
int n, a[805], 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",&a[i]);
    sort(a+1, a+n+1);
    for (int i=1; i<=n-2; i++)
       for (int j=i+1; j<n; j++)
          for (int k=j+1; k<=n; k++)
             if (a[k]<=a[i]+a[j]) ++sol;
                else k=n;
    printf("%d\n",sol);
    return 0;
}