#include <stdio.h>
int main()
{
	int n,i,j,k,nr=0;
	int a[850];
	scanf("%d",&n);
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	for (i=1; i<=n; i++)
		scanf("%d",&a[i]);
	for (i=1; i<=n-2; i++)
		for (j=i+1; j<=n-1; j++)
			for (k=j+1; k<=n; k++)
			{	if ((a[i]+a[j]>=a[k]) && (a[j]+a[k]>=a[i]) && (a[i]+a[k]>=a[j]))
					nr++;
			}
	printf("%d",nr);
	return 0;
}