#include<fstream>
#include<algorithm>
using namespace std;

int n, b[801];

int main()
{
	ifstream fin("nrtri.in");
	ofstream fout("nrtri.out");
	
	fin >> n;
	for (int i = 1; i <= n; ++i)
		fin >> b[i];
	sort(b + 1, b + n + 1);
	
	long long count = 0;
	for (int i = 1; i < n; ++i)
		for (int j = i + 1; j <= n; ++j)
		{
			int t2 = upper_bound(b + 1, b + n + 1, b[i] + b[j]) - (b + 1) - 1;
			count += t2 - j + 1;
		}
	fout << count;
		
	return 0;
}