package main

import . "fmt"

func main() {
	var a,b,c int
	Scan(&a,&b,&c)
	m:=map[int]int{}
	m[a]++
	m[b]++
	m[c]++
	if len(m)==3{
		Println(6-a-b-c)
	} else {
		Println(a^b^c)
	}
}