# coding: utf-8

N = input()
while int(N) < 1 or int(N) > 50000:
    N = input()
print(N)

D = input()
while int(D) < 0 or int(D) > 2*int(N):
    D = input()
print(D)

N = int(N) 
D = int(D)
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))