"use strict"

function main(input) {
  input = input.split(" ").map(v => ~~v)

  let ans = input[0]
  if (input[0] == input[1]) ans = input[2]
  else if (input[0] == input[2]) ans = input[1]

  console.log(ans) //
}
main(require("fs").readFileSync("/dev/stdin", "utf8"))