import java.util.Scanner

object Main {
  def main(args:Array[String]): Unit = {
    val sc = new Scanner(System.in)
    val a, b, c = sc.nextInt()

    if (a == b) {
      println(c)
    } else if (b == c) {
      println(a)
    } else {
      println(b)
    }
  }
}