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

using namespace std;

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

int main()
{
	int n,i,j;
	cin >> n;
	vector<int>v(n);
	for (i = 0; i < n; ++i)
		cin >> v[i];

	sort(v.begin(), v.end());

	int sum = 0;

	for (i = 1; i < n; ++i)
		for (j = 0; j < i; ++j)
		{
			int keresett = v[i] + v[j];
			vector<int>::iterator h = upper_bound(v.begin()+i+1, v.end(), keresett);

			sum += h - 1 - i - v.begin();
		}

	cout << sum << "\n";
}