package main

import "fmt"

func main() {
	var a, b, n int
	_, _ = fmt.Scan(&a, &b, &n)

	if n == 0 {
		fmt.Println(a)
	} else if n == 1 {
		fmt.Println(b)
	} else {
		for i := 2; i <= n; i++ {
			a, b = b, a^b
		}
		fmt.Println(b)
	}
}