#include <stdio.h>
#include <stdlib.h>

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

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]);
	/*for(i = 0; i < n-1; i++)
		for(j = i+1; j < n; j++)
			if(v[j] > v[i])
			{
				int aux = v[i];
				v[i] = v[j];
				v[j] = aux;
			}*/
	for(i = 1;i < n-1; i++)
	{
		for(j = i-1; j >= 0; j--)
		{
			for(k = i+1; k < n; k++)
				if(a[i] > 0 && a[j] >= 0 && a[k] > 0 && a[i]+a[j] >= a[k] && a[k]+a[j] >= a[i] && a[k]+a[i] >= a[j])
				{
					z++;
				}

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