ans 0 0 acc = Just acc
ans l _ acc | l <= 0 = Nothing
ans l s acc | 0 < l && s == 0 = ans (l - 1) s ('C' : acc)
ans l s acc = let v = ans (l - 1) (s - 1) ('A' : acc)
  in
  case v of
    Just val -> Just val
    Nothing -> ans (l - 1) (s - 2) ('B' : acc)
  
main = interact $ answer . map (\x -> read x :: Int) . words . head . lines
  where answer [n, m] = case ans n m [] of
          Just val -> (show . reverse) val ++ "\n"
          Nothing -> "\n"