def main():
    inp1 = list(map(int, input().split()))
    fib = [inp1[0], inp1[1]]
    
    front = fib[0] ^ fib[1]
    fib.append(front)
    
    num = inp1[2] % 3
    
    print(fib[num])    

if __name__ == '__main__':
    main()