(define $repl
        (lambda []
          (do {(let {
            [$x (unpack (io (read-line)))]} 
            (writeChar (if (equal (nth 2 x) (nth 3 x)) (nth 2 x) (nth 5 x))))
            (write "\n")}
            (repl))))

(define $main
  (lambda [$args]
    (do {[(repl)]}
      [])))