#!/usr/bin/perl

use warnings;
use strict;

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

if($a < $s) {
	$x = $s - $a;
} else {
	$x = $a - $s;
}

if($b < $s) {
	$y = $s - $b;
} else {
	$y = $b - $s;
}

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

print "$count\n";

exit;