toInt :: String -> Int
toInt = read :: String -> Int

getCharacter :: Int -> Char
getCharacter n = ['a'..'z'] !! n

solve :: Int -> String
solve n
  | n == 0 = ""
  | otherwise = solve (div (n-1) 26) ++ [getCharacter (mod (n-1) 26)]

main = do
  n <- toInt <$> getLine
  putStrLn $ solve n