sub gameOfThrones {
    my @s = split("", shift);
    my %h;
    my $cnt = 0;

    foreach (@s) {
        $h{$_}++;
    }

    foreach my $v (values %h) {
        if ($v % 2 > 0) {
            $cnt++;
        }        
    }  

    return ($cnt == 1 || $cnt == 0) ? "YES" : "NO";
}