#include <fstream.h>
#define NMAX 801
int n,l[NMAX];
long long nr;
void swap(int &x,int &y)
{ int aux;
  aux=x;
  x=y;
  y=aux;
}
int main()
{ int i,j,k;
  ifstream f("nrtri.in");
  f>>n;
  for (i=1;i<=n;i++) f>>l[i];
  f.close();
  for (i=1;i<n;i++) for (j=i+1;j<=n;j++)if (l[i]>l[j]) swap(l[i],l[j]);
  for (i=1;i<n;i++)
	for (j=i+1;j<=n;j++)
		{ for (k=j+1;k<=n&&l[k]<=l[i]+l[j];k++) ;
		  k--;
		  nr+=k-j;
		}
  ofstream g("nrtri.out");
  g<<nr;
  g.close();
  return 0;
}