import Data.Char

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