def main():
    f_0, f_1, n = [int(i) for i in input().split()]

    if n % 3 == 0:
        ans = f_0
    elif n % 3 == 1:
        ans = f_1
    elif n % 3 == 2:
        ans = f_0 ^ f_1

    print(ans)


if __name__ == "__main__":
    main()