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