import Control.Applicative ((<$>))
import Data.List (unfoldr)
import Data.Char (ord, chr)

main :: IO ()
main = solve <$> readLn >>= putStrLn

solve :: Int -> String
solve n = reverse $ unfoldr f (n+1)
  where f x | x == 0 = Nothing
            | r == 0 = Just ('Z', q-1)
            | otherwise = Just (chr (ord 'A' - 1 + r), q)
              where (q, r) = divMod x 26