import Data.Char
import Data.Int

main :: IO ()
main = do
    xs <- getLine
    let n :: Integer
        n = read xs
    let fff :: Integer -> [Char] -> [Char]
        fff tmp xs = let a = tmp `div` 26 in if a == 0 then (chr (fromI (96+tmp`mod`26))):xs else fff a ((chr (fromI (96+tmp`mod`26))):xs)
    putStrLn $ fff n []

fromI :: Integer -> Int
fromI = fromInteger