DECLARE FUNCTION Rot13$ (S AS STRING)
DIM S AS STRING

INPUT "", S
WHILE S <> ""
	PRINT Rot13$(S)
	INPUT "", S
WEND

FUNCTION Rot13$ (S AS STRING)
	DIM I, J AS INTEGER
	DIM T AS STRING

	FOR I = 1 TO LEN(S)
		J = ASC(MID$(S, I, 1))
		IF J >= 65 AND J <= 90 THEN
			J = ((J - 52) MOD 26) + 65
		ELSEIF J >= 97 AND J <= 122 THEN
			J = ((J - 84) MOD 26) + 97
		END IF
		T = T + CHR$(J)
	NEXT I
	Rot13$ = T
END FUNCTION