#!/usr/bin/perl

use strict;
use warnings;

my ($x, $y, $d) = split / /, <>;
my $count = 0;

if($y < $x) {
	($x, $y) = ($y, $x);
}

if($d < $x) {
	$count = $d + 1;
} elsif(($x <= $d)and($d <= $y)) {
	$count = $x + 1;
} elsif($d <= $x + $y) {
	$count = $x + $y + 1 - $d;
} 

print "$count\n";

exit;