N,D = map(int,input().split())
ans = []
for i in range(N):
	if D > 0 and (N - i) * 2 > D:
		ans.append('A')
		D-=1
	elif D > 1 and (N - i) * 2 == D:
		ans.append('B')
		D-=2
	else:
		ans.append('C')
print(''.join(ans))