main :: IO ()
main = do
  [n, d] <- map read . words <$> getLine
  putStrLn $ solve n d

solve :: Int -> Int -> String
solve n d = solve' n d ""
  where solve' :: Int -> Int -> String -> String
        solve' 0 _ s = s
        solve' n' d' s
          | n' < d' = solve' (n' - 1) (d' - 2) ('B':s)
          | n' == d' = replicate n' 'A' ++ s
          | n' > d' = solve' (n' - 1) d' ('C':s)