use feature 'say';
$n=<>;
if(fork){
	$z="z"x$n;
	$o=<>;
	for$i(0..$n-1){
		for$c("b".."y"){
			$r=<>;
			if($r>$o){
				substr($z,$i,1)=$c;
			}
			if($r<$o){
				substr($z,$i,1)="a";
			}
		}
	}
	say "! $z";
}else{
	$|=1;
	say "? ","a"x$n;
	for$i(0..$n-1){
		for$c("b".."y"){
			say "? ","a"x$i,$c,"a"x($n-$i-1);
		}
	}
}