#!/usr/bin/perl

use strict;
use warnings;

my ($x, $y, $d) = split / /, <>;
my $count = 0;
for(my $i = 0; $i <= $x; $i++) {
	for(my $j = 0; $j <= $y; $j++) {
		if($i + $j == $d) {
			$count++;
		} 
	}
}

print "$count\n";

exit;