//NRTRI, versiunea cu sortare + cautare liniara
#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <limits>
using namespace std;

int main() {
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");
	vector <int> v;
	int n, nr, i, j, k, rez=0;
	f>>n;
	for(i=1; i<=n; i++) {
		f>>nr;
		v.push_back(nr);
	}
	
	v.push_back(INT_MAX);
	sort(v.begin(), v.end());
	
	for(i=0; i<n-1; i++) {
		for(j=i+1; j<n; j++) {
			k=j+1;
			while(v[k]<=v[i]+v[j]) {
				k++; rez++;
			}
		}
	}
	g<<rez;
	
	
	f.close();
	g.close();
	return 0;
}