main = solve . head . map read . words <$> getLine >>= putStrLn

cs = ['a'..'z']

at 0 (c:_) = c
at n (_:l) = at (n-1) l

solve n = reverse $ solve' (n-1)

solve' :: Integer -> String
solve' n
    | n < 26   = [at n' cs]
    | otherwise = at n' cs : solve' n''
    where
        n'  = n `mod` 26
        n'' = n `div` 26 - 1