input_list = input().split()

N = int(input_list[0])
D = int(input_list[1])

def calc(n, d):
  ans = []
  while True:
    if n <= 0:
      ans.sort()
      return "".join(ans)

    if d == n:
      ans.append('A')
      d = d - 1
      n = n - 1
    elif d > n:
      ans.append('B')
      d = d - 2
      n = n - 1
    else:
      ans.append('C')
      n = n - 1

print(calc(N, D))