#include <iostream>
# include <fstream>
# include <cstdio>
# include <algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int n;
 int v[800];
int cauta(int x)
{
    int i,pas = 1<<10;
    for(i =0; pas!=0;pas/=2)
        if(i+pas<n && v[i+pas] <= x)
            i+= pas;
    return i;
}

int main()
{

    in>>n;

    int nr;
    int rez =0;
    for(int i = 0; i<n;i++)
        in>>v[i];
    sort(v,v+n);
    for(int i= 0;i<n;i++)
        for(int f=i+1;f<n;f++)
            {
                nr = cauta(v[i]+v[f]);
                rez += nr-f;
            }
     out<<rez;
    return 0;
}