#!/usr/bin/perl -w

use strict;

sub sq {
  my ($n, $o, $i);
  $n = shift;
  $i = 0;
  $o = 1;
  $n *= 1000000;

  while ($n - $o > 0) {
    $n -= $o;
    $o += 2;
    $i++;
  }

  print(($i / 1000), "\n");
}

&sq(2);