#!/usr/bin/perl

use warnings;
use strict;

my ($a, $b, $s) = split / /, <>;
my $x = $a - $s;
my $y = $b - $s;
my $count = 0;

if($x < 0) {
	$x *= -1;
}

if($y < 0) {
	$y *= -1;
}

if($a <= $b) {
	$count = $x + $s;
} else {
	$count = $y;
	$y = $a - $b;
	if($y < 0) {
		$y *= -1;
	}
	if($a < $y) {
		$count += $a;
	} else {
		$count += $y + $a;
	}
}

print "$count\n";

exit;