#include<fstream>
#include<iostream>
#include<algorithm>
using namespace std;
int v[801],n,a1,a2,a3,x;
int main()
{
	ifstream fin("nrtri.in");
	ofstream fout("nrtri.out");
	fin>>n;
	for(a1=1;a1<=n;a1++)
		fin>>v[a1];
	sort(v+1,v+n+1);
	for(a1=1;a1<=n-2;a1++)
		for(a2=a2+1;a2<=n-1;a2++)
			for(a3=a2+1;a3<=n;a3++)
			{
				if(v[a1]+v[a2]>v[a3])
					x++;
				else break;
			}
	fout<<x;
				
	
}