import Data.Char
import Data.List

main = readLn >>= putStrLn . reverse . map (chr . (+65)) . unfoldr divmod

divmod (-1) = Nothing
divmod n = case divMod n 26 of
 (0,0) -> Just (0,-1)
 (0,m) -> Just (m,-1)
 (d,m) -> Just (m,d-1)