fun readfile () = readfile []
           | x = let val ln = readln ()
                 in if eof ln then
                      rev x
                    else
                      readfile ` ln :: x
                 end

local
	val lower_z = ord #"z";
	val upper_z = ord #"Z";
	val lower_a = ord #"a";
	val upper_a = ord #"A";
	
	fun which
			(c_upper c) = (upper_a, upper_z)
		|	_	    = (lower_a, lower_z)
		;
	
	fun scale
			(c, az) where (c > #1 az) = scale( (#0 az + (c - #1 az - 1)), az)
		|	(c, az) 		  = c
			
in
	fun rot13
			([], t) 			    = implode ` rev t
		|	(x :: xs, t) where (c_alphabetic x) = rot13 (xs, (chr ` scale (ord x + 13, which x)) :: t)
		|	(x :: xs, t)                        = rot13 (xs, x :: t)
		|	s 				    = rot13 (explode s, [])
end;

map (println o rot13) ` readfile ();