N, D = map(int, raw_input().split())
B = D/2
A = D%2
C = N-A-B
while True:
	if B == 0 or C == 0:
		break
	A += 2
	B -= 1
	C -= 1
ans = ''
for i in range(0, A):
	ans = ans + 'A'
for i in range(0, B):
	ans = ans + 'B'
for i in range(0, C):
	ans = ans + 'C'
print ans