use strict;
	use warnings;

	use utf8;
	use Data::Dumper;
	use Encode qw/encode decode decode_utf8 encode_utf8 from_to/;

my $inp = decode('utf8', <STDIN>);
my @array = split(" ", $inp);
my($a ,$b) = @array;
while ($b != 0)
{
    my $c = ($a & $b) << 1;
    $a ^= $b;
    $b = $c;
}
print $a;