during normal walk forest Katie stumble mysterious code however mysterious code character unreadable she write code string c consist lowercase english character asterisk asterisks denote unreadable character excite discovery Katie decide recover unreadable character replace asterisk arbitrary lowercase english letter different asterisk replace different letterskatie favorite string s notsofavorite string t love recover mysterious code occurrence s possible little occurrence t possible Formally let denote fx y number occurrence y x example faababa ab 2 Katie want recover code c conform original c fc s fc t large possible However Katie good recover code general like help