import Data.Char (chr, ord)

l :: Int
l = length ['A'..'Z']

main :: IO ()
main = putStrLn . solve =<< readLn

solve :: Int -> String
solve = alphabet . solve'

solve' :: Int -> [Int]
solve' n = solve'' n []

solve'' :: Int -> [Int] -> [Int]
solve'' n xs = if d == 0 then xs' else solve'' (d - 1) xs'
        where (d, m) = n `divMod` l
              xs' = (m:xs)

alphabet :: [Int] -> String
alphabet = map (chr . (+ (ord 'A')))