(defun fib (n)
  (labels ((rec (a b c p q)
                (cond ((zerop c)
                        b)
                      ((evenp c)
                        (rec a b (floor c 2) (+ (* p p) (* q q)) (+ (* 2 p q) (* q q))))
                      (t
                        (rec (+ (* b q) (* a q) (* a p)) (+ (* b p) (* a q)) (1- c) p q)))))
    (rec 1 0 n 0 1)))

(defun main (&rest argv)
  (declare (ignorable argv))
  (format t "~d~%" (fib (1+ (read)))))

(main)