#include <fstream>
#include <algorithm>
using namespace std;
const char iname[] = "nrtri.in";
const char oname[] = "nrtri.out";
ifstream fin(iname);
ofstream fout(oname);
int N, i, j, k, ANS, x, last_poz;
int v[804];
int main()
{
	fin >> N;
	for (i = 1; i <= N; ++i) fin >> v[i];
	sort (v + 1, v + N + 1);
	for (i = 1; i <= N; ++i)
	{
		last_poz = i + 1;
		for (j = i + 1; j <= N; ++j)
		{
			x = v[i] + v[j];
			for (k = last_poz; k <= N; ++k) 
				if (v[k] <= x) last_poz = k;
				else 
					break;
			ANS += (last_poz - j);
		}
	}
	fout << ANS << '\n';
	return 0;
}