N,D = map(int,input().split())
ans = ""
if N == D:
	for n in range(N):
		ans = ans + "A"
elif N < D:
	for d in range(D - N):
		ans = ans + "B"
	for n in range(2 * N - D):
		ans = "A" + ans
else:
	for d in range(D):
		ans = ans + "C"
	for n in range(N - D):
		ans = "A" + ans
print(ans)