import Control.Monad

rconv :: Integral a => a -> Bool -> [a]
rconv n f
    |     f && n < 26 = [n]
    | not f && n < 27 = [pred n]
    |     f           = rconv (n `div` 26) False ++ [n `mod` 26]
    | not f           = rconv (n `div` 27) False ++ [n `mod` 27]

cconv :: Integral a => a -> Char -> Char
cconv 0 c = c
cconv n c = cconv (pred n) (succ c)

solve :: Integral a => a -> [Char]
solve n = [cconv t 'A' | t <- rconv n True]

main = do
    n <- readLn
    putStrLn $ solve n