#include <fstream>
#include <algorithm>

using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

long long n, v[805];
long long a, b, c, nr = 0;

int main()
{
	fin >> n;
	for (long long i = 1; i <= n; i++)
	{
		fin >> v[i];
	}
	sort(v + 1, v + n + 1);
	for (int a = 1; a <= n - 2; a++)
	{
		for (int b = a + 1; b <= n - 1; b++)
		{
			for (int c = b + 1; c <= n; c++)
			{
				if (v[a] + v[b] >= v[c] && v[a] + v[c] >= v[b] && v[b] + v[c] >= v[a])
				{
					nr++;
				}
				if (v[a] + v[b] < v[c])
				{
					break;
				}
			}
		}
	}
	fout << nr;
}