$|=1;
$a=0;
$b=1001;
while($a<$b-1){
	$c=$a+$b>>1;
	print"? $c\n";
	if(<>=~out){
		++$c;
		print"? $c\n";
		if(<>=~out){
			$b=$c-1;
		}else{
			$a=$c;
		}
	}else{
		$a=$c;
	}
}
print"! $a\n"