#include <stdio.h>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
#define RRR ios_base::sync_with_stdio(false);cin.tie(0);
#define ll long long

#define pp pair<int,int>
using namespace std;
int ar[900];

int main()
{
	RRR
		//			freopen("text.txt","r",stdin);
	//	int i,j,q,a,x;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	
	int n;
	cin >> n;
	for (int i=1;i<=n;i++)
	{
		cin >> ar[i];
	}
	int s = 0;
	sort(ar+1,ar+n);
	for (int i=1;i<=n;i++)
	{
		for (int j=i+1;j<=n;j++)
		{
			for (int k=j+1;ar[k] <= ar[i] + ar[j] && k<=n;k++)
			{
				
					s++;
			}
		}
	}
	cout << s;//;
	return 0;
 
}