import scala.io.StdIn._
import scala.math._
 
object Main extends App{
  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)
  }
}