#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

ifstream cin("nrtri.in");
ofstream cout("nrtri.out");

int main()
{
	int n, x;
	vector < int > v;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> x;
		v.push_back(x);
	}
	sort(v.begin(), v.end());

	int nr = 0;

	for (int i = 0; i < n; i++)
	{
		for (int j = i + 1; j < n; j++)
		{
			int up = upper_bound(v.begin(), v.end(), v[i] + v[j]) - v.begin();
			nr += up - 1 - j;
		}
	}
	cout << nr;
	return 0;
}