(ns competitive.clj
  (:require [clojure.string :as str]))

(defn read-split
  []
  (str/split (read-line) #" "))

(defn to-long
  "Convert string to long"
  [s]
  (Long/parseLong s))

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

(defn third
  [x]
  (first (next (next x))))

(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)))))

(defn -main
  []
  (println (one-out-of-three)))

(-main)