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

using namespace std;

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

int n,v[801],i,j,x,rez;
int main()
{
    fin>>n;
    for(i=1; i<=n; i++)
        fin>>v[i];
    sort(v+1,v+n+1);
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
            for(x=j+1; x<=n && v[x]<=v[i]+v[j]; x++)
                    rez++;
    fout<<rez;

    fin.close();
    fout.close();
    return 0;
}