sub solve{
    my( $a, $b, $c, $d ) = @_;
    my( $x, $y );

    $x = ($b - $a) / ($d - $a - $c + $b);
    $y = ($d - $a) * ($b - $a) / ($d - $a - $c + $b) + $a;
    
    return( $x, $y );
}