#include<fstream.h>

unsigned int v[801];
int i, j, k, contor, n;

void citire()
{
  ifstream in("nrtri.in");
  in>>n;
  for(i=1; i<=n; i++)
    in>>v[i];
  in.close();
}
  
void prelucr()
{
  for (i=1; i<n-1; i++)
    for (j=i+1; j<n; j++)
      for (k=j+1; k<=n; k++)
	if (v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i]) contor++;
  ofstream out("nrtri.out");
  out<<contor;
  out.close();
}
 
int main()
{
   citire();
   prelucr();
   return 0;
}