# coding: utf-8

N = input("文字数入力    >>> ")
while int(N) < 1 or int(N) > 50000:
    N = input("文字数は1以上50000以下にしてください。文字数を再入力    >>> ")
print("文字数：", N)

D = input("穴数を入力    >>> ")
while int(D) < 0 or int(D) > 2*int(N):
    D = input("穴数は0以上2×文字数以下にしてください。穴数を再入力    >>> ")
print("穴数：", D)

N = int(N) #文字数
D = int(D) #穴数
alfabetArr = ["A","B","C"]

def generateAns(N, D):
    if N < D:
        numB = D - N
        numA = N - numB
        numC = 0
    elif N == D:
        numA = N
        numB = 0
        numC = 0
    else:
        numA = N - D
        numC = N - numA
        numB = 0

    answer = ""
    for i in range(numA):
        answer += str(alfabetArr[0])
    for j in range(numB):
        answer += str(alfabetArr[1])
    for k in range(numC):
        answer += str(alfabetArr[2])
    return answer

print(generateAns(N, D))