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

using namespace std;

int main()
{
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,i,a[801],y,j,nr=0;
fin >>n;
for (i=1;i<=n;++i){
fin>>a[i];
}
sort(a+1,a+n+1);
for (i=1;i<=n-2;i++){
        for (j=i+1;j<=n-1;j++){
            for (y=j+1;y<=n;y++){
                if (a[y] <= a[i] + a[j])
                   {

                   nr++;}
                else
                   break;

            }
        }
    }
    fout << nr;

    return 0;
}