#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <algorithm>

using namespace std;


int main()
{
	freopen("nrtri.in", "rt", stdin);
	freopen("nrtri.out", "wt", stdout);

	int n;
	scanf("%d", &n);
	int *v = new int[n];

	for (int i = 0; i < n; i++)
		scanf("%d", v + i);

	sort(v, v + n);
	long long s = 0;

	for (int i = 0; i < n; i++)
		for (int j = i + 1; j < n; j++)
			s += upper_bound(v + j + 1, v + n, v[j] + v[i]) - lower_bound(v + j + 1, v + n, v[j] - v[i]);

	printf("%Ld\n", s);

	return 0;
}