def ana(N, D):
    if D == 0:
        S = 'C' * N
        return S
    else:
        for i in range(N + 1):
            a = N - i
            if (2 * N - D - a >= 0) and (D - a >= 0) and ((2 * N - D - a) % 2 == 0) and ((D - a) % 2 == 0):
                b = (D - a) // 2
                c = (2 * N - D - a) // 2
                break
        S = 'A' * a + 'B' * b + 'C' * c
        return S

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

if __name__ == '__main__':
    main()