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

    x = D // N
    if x == 2:
        ans = 'B' * N
    elif x == 0:
        etc = N - D
        ans = 'A' * D + 'C' * etc
    if x == 1:
        two = D - N
        one = N - two
        ans = 'A' * one + 'B' * two

    print(ans)

main()