$h[$_]=rand,$H[$_]=rand for 1..<>;
$h{0}{0}=0;
	($q,$L,$R,$K)=glob,
	'!'eq$q?
		$h{$h+=$K*($h[$L]-$h[$R])}{$H+=$K*($H[$L]-$H[$R])}//=$.-1
	:
		print$h{$h}{$H}+0,$/
while<>