#!/usr/bin/env perl

use strict;
use warnings;

my $n = <>; chomp $n;
my $r = int(sqrt($n / 3));
for (my $d = -1000000; $d < 1000000; $d++) {
  if (abs(($r + $d) * ($r + $d) * 3 - $n) <= 1000000) {
    if ($r + $d > 0) {
      print $r + $d;
      exit;
    }
  }
}