N, D = map(int, input().split())

for a in range(min(N, D), -1, -1):
    if (D - a) % 2 != 0:
        continue
    b = (D - a) // 2
    if a + b > N:
        continue
    print(a * "A" + b * "B" + (N - a - b) * "C")
    exit()