def main():
    f_0, f_1, n = [int(i) for i in input().split()]
    sequence_list = [f_0, f_1]
    for i in range(2, n + 1):
        sequence_list.append(sequence_list[i - 2] ^ sequence_list[i - 1])
    print(sequence_list[n])


if __name__ == "__main__":
    main()