#include <vector>
#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;

int main(){
	ifstream f("nrtri.in");
	int n = 0;
	f >> n;
	vector<int> v(n, 0);
	for(auto& x : v){
		f >> x; }
	sort(begin(v), end(v));
	unsigned long long rez = 0;
	for(auto it = begin(v); it != end(v); ++it){
		for(auto it2 = it+1; it2+1 < end(v); ++it2){
			auto it3 = upper_bound(it2+1, end(v), *it + *it2);
			rez += it3 - it2 - 1; } }
	ofstream g("nrtri.out");
	g << rez << '\n';
	return 0; }