import sequtils, strutils

let
  nd = stdin.readLine.split.map parseInt
  n = nd[0]
  d = nd[1]

echo:
  if n == d: 'A'.repeat n
  elif n > d: 'A'.repeat(d) & 'C'.repeat(n - d)
  else: 'A'.repeat(n * 2 - d) & 'B'.repeat(n - n * 2 + d)