#include <fstream>
#include <algorithm>
using namespace std;
 
ifstream f("nrtri.in");
ofstream g("nrtri.out");
 
int n, a[805], sol;
 
int main()
{
    f>>n;
    for (int i=1; i<=n; i++) f>>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;
    g<<sol<<'\n';
    return 0;
}