#include <stdio.h>
int main ()
{FILE *f=fopen("nrtri.in","r");
FILE *g=fopen("nrtri.out","w");
int n,i,j,k,nr=0,v[801],ok,aux;
fscanf (f,"%d",&n);
for (i=1; i<=n; i++)
	fscanf (f,"%d",&v[i]);
do{ok=1;
   for (i=1; i<n; i++) 
	   if (v[i]>v[i+1]) {ok=0;
				   aux=v[i];
				   v[i]=v[i+1];
				   v[i+1]=aux;
				   }
	}
while (ok==0);

for (i=1; i<=n-2; i++)
	for (j=i+1; j<=n-1; j++)
			{ k=j+1;
			  while  (v[i]+v[j]<v[k] && v[i]+v[k]<v[j] && v[j]+v[k]<v[i]) k++;
			  nr=nr+n-k+1;}
fprintf (g,"%d",nr);
fclose (f);
fclose (g);
return 0;
}