#include <iostream>
#include <limits.h>
#include <cmath>
#include <string>
#include <stdio.h>
#include <algorithm>
#include <stdlib.h>
#include <vector>
#include <stack>
#include <map>
#include <fstream>
#include <list>
#include <queue>
#include <iomanip>
#include <deque>
#include <set>

using namespace std;

#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define PI 3.14159265
#define mm 500005
#define inf 2*1000000000

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

int v[805];

int main()
{
    int n;
    f >> n;

    for(int i = 1; i <= n; i++)
        f >> v[i];

    sort(v+1,v+n+1);

    int ans = 0;
    for(int i = 1; i <= n-2; i++)
        for(int j = i+1; j <= n-1; j++)
            for(int k = j+1; k <= n && v[i] + v[j] >= v[k]; k++)
                    ans++;

    g << ans;

    return 0;
}