#include <stdio.h>
#include <algorithm>
using namespace std;

int cmp (int a, int b)
{
	return (a<b);
}

int main ()
{
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out", "w", stdout);
	int n, i, j, s, nr=0, v[801];
	scanf("%d", &n);
	for (i=1; i<=n; i++) {
		scanf("%d", &v[i]);
	}
	sort (v+1, v+n+1, cmp);
	for (i=1; i<n-1; i++) {
		s=v[i]+v[i+1];
		for (j=i+2; j<=n; j++) {
			if (s>=v[j]) {
				nr++;
			} else {
				break;
			}
		}
	}
	printf("%d", nr);
	return 0;
}