object Main{
  def main(args:Array[String]) = {
    val sc = new java.util.Scanner(System.in)
    val a = sc.nextInt;
    val b = sc.nextInt;
    val c = sc.nextInt;
    if(a == b){
      println(c)
    }else if(a == c){
      println(b)
    }else{
      println(a)
    }
  }
}
