-- yukicoder My practice
-- author: Leonardone @ NEETSDKASU

main = putStrLn . solve . map read . words =<< getLine

solve [n, d] = hoge n d where
    hoge n d
         | n >= d = replicate d 'A' ++ replicate (n - d) 'C'
         | n < d  = replicate (n - bs) 'A' ++ replicate bs 'B'
         where
            bs = d - n