package main

import (
	"fmt"
)

func main() {
	var F0, F1, N int
	fmt.Scan(&F0, &F1, &N)
	switch N % 3 {
	case 0:
		fmt.Println(F0)
	case 1:
		fmt.Println(F1)
	case 2:
		fmt.Println(F0 ^ F1)
	}
}