(loop for char = (read-char nil nil)
      while char do
        (if (char= char #\Newline) (return))
        (if (upper-case-p char) (format 't "~A" (string-downcase char)))
        (if (lower-case-p char) (format 't "~A" (string-upcase char)))
        ;(format t "input: ~A~%" char) )
)
(format 't "~%")