package zh.codegym.task.task04.task0424;
/*
三个数字
*/
import java.io.*;
public class Solution {
public static void main(String[] args) throws Exception {
BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));
String num1 = buffer.readLine();
int a = Integer.parseInt(num1);
String num2 = buffer.readLine();
int b = Integer.parseInt(num2);
String num3 = buffer.readLine();
int c = Integer.parseInt(num3);
if(a==b)
System.out.println(c);
if(a==c)
System.out.println(b);
if(b==c)
System.out.println(a);
}
}