mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    N, D = map(int, input().split())
    ans = ["A"] * N
    if D < N:
        for i in range(N - D):
            ans[-i-1] = "C"
    elif D > N:
        for i in range(D - N):
            ans[-i-1] = "B"
    print("".join(ans))


if __name__ == '__main__':
    main()