#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");
int n,a[801],i,j,k,sol;
int main()
{ fi>>n;
  for(i=1;i<=n;i++) fi>>a[i];
  sort(a+1,a+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 (a[i]+a[j]>=a[k]) sol++;
                           else break;
  fo<<sol;
    return 0;
}