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

int a[1000], n, i, j, sol;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d", &n);
	for (i = 1; i <= n; ++ i)
		scanf("%d", &a[i]);
	sort(a+1, a+n+1);
	for (i = 1; i <=n; ++ i)
		for (j = i+1; j <= n; ++ j)
		{
			sol+=(int)(lower_bound(a+1,a+n+1,a[i]+a[j])-a)-j-1;
		}
	printf("%d\n", sol);
	return 0;
}