(defn read-number
  []
  (map to-long (read-split)))

(defn one-out-of-three
  []
  (let [nums (read-number)]
    (if (= (first nums) (second nums))
      (third nums)
      (if (= (first nums) (third nums))
        (second nums)
        (first nums)))))

(println (one-out-of-three))