import Control.Applicative ((<$>))

main :: IO ()
main = solve <$> map read <$> words <$> getLine >>= putStrLn

solve :: [Int] -> String
solve [n, d] | d <= n = replicate d 'A' ++ replicate (n - d) 'C'
             | otherwise = replicate (2 * n - d) 'A' ++ replicate (d - n) 'B'