sub kangaroo {
    my $kangaroo1Start = shift;
    my $kangaroo1JumpLength = shift;
    my $kangaroo2Start = shift;
    my $kangaroo2JumpLength = shift;

    my $startDistance = $kangaroo1Start - $kangaroo2Start;
    my $jumpDifference = $kangaroo2JumpLength - $kangaroo1JumpLength;

    if ($jumpDifference == 0) {
        return $startDistance == 0 ? "YES" : "NO";
    }

    if ($startDistance / $jumpDifference < 0) {
        return "NO";
    }

    return $startDistance % $jumpDifference == 0 ? "YES" : "NO";
}