def main():
    N, D = map(int, input().split())

    if N <= D:
        two_num = D - N
        one_num = D - (two_num * 2)
        print("A"*one_num + "B"*two_num)
    else:
        print("A"*D + "C"*(N-D))



if __name__ == "__main__":
    main()