# coding: utf-8

inpt = input()
x = inpt.split(" ")
N = x[0]
D = x[1]

N = int(N) 
D = int(D)
alfabetArr = ["A","B","C"]

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

    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))