#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;

int main()
{
	int n,i,nr,d,j,v[805];
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");

	f>>n;
	nr=0;
	for(i=1;i<=n;i++)f>>v[i];
	sort(v+1,v+n+1);
	
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<n;j++)
			for(d=j+1;d<=n;d++)
				if (v[i]+v[j]>=v[d])nr++;else break;
		
	g<<nr;
	
	return 0;



}