main = do
    n <- getLine >>= return . read
    putStr $ f n

f n = if n < 27 
        then toAlp n
        else if y == 0
            then f (x - 1) ++ "z"
            else f x ++ toAlp y
                where
                    x = div n 26
                    y = mod n 26

toAlp 0 = "z"
toAlp x = [(['a'..'z'] !! (x-1))]