MODULE Rot13 EXPORTS Main;

IMPORT Stdio, Rd, Wr;

VAR c: CHAR;

<*FATAL ANY*>

BEGIN
  WHILE NOT Rd.EOF(Stdio.stdin) DO
    c := Rd.GetChar(Stdio.stdin);
    IF c >= 'A' AND c <= 'M' OR c >= 'a' AND c <= 'm' THEN
      c := VAL(ORD((ORD(c) + 13)), CHAR);
    ELSIF c >= 'N' AND c <= 'Z' OR c >= 'n' AND c <= 'z' THEN
      c := VAL(ORD((ORD(c) - 13)), CHAR);
    END;
    Wr.PutChar(Stdio.stdout, c);
  END;
END Rot13.