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

using namespace std;

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

int n,v[805],i,j,ct,k;

int main()
{
    in>>n;

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

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

    for(i=1;i<=n-2;i++) {
        for(j=i+1;j<=n-1;j++) {

            int cbr = upper_bound(v+j+1, v+n+1, v[i] + v[j]) - v-1;
            ct += cbr-j;

        }
    }

    out<<ct;


    return 0;
}
// 2 3 4 4 5 7