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

s = ""

if N == D:
  s = "A"*N
elif N > D:
  s = "A"*D
  s += "C"*(N-D)
else:
  if D-N == 1:
    s = "A"*(N-1)
    s += "B"
  else:
    s = "A"*(2*N-D)
    s += "B"*(D-N)

print(s)