#include <fstream>
#include <algorithm>
using namespace std;
int x[801], i, n, j, s;
int main()
{
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");
	f>>n;
	for(i=1; i<=n; i++)
	{
		f>>x[i];
	}
	sort(x+1, x+n+1);
	for(i=1; i<=n; i++)
	{
		for(j=i+1; j<=n; j++)
		{
			s=s+(x-lower_bound(x+j+1, x+n+1, x[j]-x[j]))-(x-upper_bound(x+j+1, x+n+1, x[j]+x[i]));
		}
	}
	g<<s;
}