changeIntToChar n = ['a'..'z'] !! n
solve :: [Char] -> Int -> [Char]
solve ans n
 | n < 27    = tmp
 | otherwise = solve tmp ((n - 1) `div` 26)
  where tmp = (changeIntToChar((n - 1) `mod` 26)):ans
main = putStr =<< (solve []) . read <$> getLine