#include <iostream.h>
#include <fstream.h>

   fstream f("nrtri.in",ios::in);
   fstream g("nrtri.out",ios::out);
   int a[801];
   int main()
     {
     int m, n,i,j,aux,k=0, ok;
	   f>>n;
       for (i=1;i<=n;i++)
	  {
	  f>>a[i];
	  }
      do{
	ok=1;
	for(i=1;i<n;i++)
	{
	  if(a[i]>a[i+1])
	  {
	   aux=a[i];
	   a[i]=a[i+1];
	   a[i+1]=aux;
	   ok=0;
	   }
	}
       }while(!ok);

	for(i=1;i<=n-2;i++)
	for(j=i+1;j<=n-1;j++)
	for(m=j+1;m<=n;m++)
	  {
	   if ((a[i]+a[j])>=a[m] )

		k++;
	    }
	    g<<k;
	    f.close();
            g.close();
	return 0;
      }