#include <iostream>
#include <fstream>
using namespace std;
int main()
{ifstream fin("nrtri.in");
 ofstream fout("nrtri.out");
 int a[801],k,n,i,contor=0,j;
 fin>>n;
 for(i=1; i<=n; i++)
    fin>>a[i];
 for(i=1; i<=n; i++)
    for(j=i+1; j<=n; j++)
       for(k=j+1; k<=n; k++)
          if(a[i]+a[j]>=a[k] && a[j]+a[k]>=a[i] && a[i]+a[k]>=a[j])
          contor++;
       fout<<contor;
}