Who comes in?

          Who comes in must      come out.

          Who comes in must be surprised.

ThoseWho comes in must be surprised.

Those          comingin must be surprised.

Any              comingin must be surprised.

  If you come in, you  must be surprised.

(Ai đi vào chắc phải đi ra)
(Ai đi vào chắc bị ngac nhiên.)