#include <cstdio>
#include <algorithm>

using namespace std;
int a[801];
int n;

int main ()
{
	freopen ("nrtri.in", "r", stdin);
	freopen ("nrtri.out", "w",stdout);
	scanf ("%d ", &n);
	int i, j,k;
	for (i = 1; i <= n; ++i)
		scanf ("%d ", &a[i]);
	
	sort (a + 1, a + n + 1);

	k = 0;
	int rez = 0;

	for (i = 1; i <= n; ++i)
		for (j = i + 1; j <= n; ++j)
		{
			for (k = max (k, j + 1); k <= n && a[i] + a[j] >= a[k]; ++k);
				
			
			--k;
			rez += k - j;
		}

	printf ("%d\n", rez);
	return 0;
}