#include <cstdio>
#include <stdlib.h>
#include <algorithm>

using namespace std;

int a[1001], i, j, k, z, n, ok, aux;

int main()
{
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out", "w", stdout);

	scanf("%d", &n);
	for(i = 0; i < n; i++)
		scanf("%d", &a[i]);
	sort(a, a + n);
	for(i = 0; i < n; i++)
	{
		for(j = i+1; j < n; j++)
		{
			ok = 0;
			for(k = j+1; k < n && !ok; k++)
				if(a[i] + a[j] >= a[k])
				{
					z++;
				}
				else
					ok = 1;

		}
	}
	printf("%d", z);
	
	return 0;
}