main :: IO ()
main = do
    [n,d] <- map read . words <$> getLine :: IO [Int]
  
    let ans = if d <= n then
                take d (repeat 'A') ++ take (n-d) (repeat 'C')
              else
                take (2*n-d) (repeat 'A') ++ take (d-n) (repeat 'B')
  
    putStrLn $ ans