<?php

fscanf(STDIN, "%d %d %d", $a, $b, $s);


$zetaia=abs($a-$s);
$zetaib=abs($b-$s);

if($s==1){
	if($a==0){
		$i=2;
	}else{
		$i=$a;
	}
}elseif($a==0 and $zetaia>$zetaib){
	$i=$zetaib+$s+1;
}elseif($zetaia<=$zetaib){
	$i=$zetaia+$s;
}else{
	if($zetaia<$s-1){
		$i=$zetaib+$zetaia+$a;	
	}else{
		$i=$zetaib+$s-1+$a;

	}

}


echo $i."\n";

?>