(defn LucasNumber [N]
  (case N
    0 (bigint 2)
    1 (bigint 1)
    (+ (LucasNumber (dec N)) (LucasNumber (dec (dec N))))))

(def LucasNumber (memoize LucasNumber))

(->> (read)
  int
  LucasNumber
  (printf "%s\n"))