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

//Constante
const int MAX_SIZE = 801;
ifstream in("nrtri.in");

//Variabile
ofstream out("nrtri.out");

int n, nminus1;
int triunghiuri;
int v[MAX_SIZE];

//Main
int main()
{
	in >> n;
	nminus1 = n - 1;
	
	for(int i=1 ; i<=n ; ++i)
		in >> v[i];
	
	sort(v+1, v+n+1);
	
	for(int i=1 ; i<nminus1 ; ++i)
		for(int j=i+1 ; j<n ; ++j)
			triunghiuri += upper_bound(&v[j]+1, v+n+1, v[i]+v[j]) - &v[j+1];
	
	out << triunghiuri;
	
	in.close();
	out.close();
	return 0;
}