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

using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

int v[1000], N;

int main()
{
	int i, j, k, nr = 0;
	
	f >> N;
	
	for(i = 1; i <= N; ++i)
		in >> v[i];
	
	sort(v + 1, v + N + 1);
	
	for(i = 1; i <= N; ++i)
		for(j = i + 1; j <= N; ++j)
			for(k = j + 1; k <= N; ++k)
				if(v[i] + v[j] >= v[k])
					++nr;
				else
					break;
				
	out << nr;
	
	return 0;
}