package main

import (
	"fmt"
)

func resolve(F0, F1, N int64) int64 {
	switch N % 3 {
	case 0:
		return F0
	case 1:
		return F1
	case 2:
		return F0 ^ F1
	}
	// Unreachable
	return -1
}

func main() {
	var F0, F1, N int64
	fmt.Scanf("%d %d %d\n", &F0, &F1, &N)
	fmt.Println(resolve(F0, F1, N))
}