sborDelenie :: Int -> Int -> IO ()
sborDelenie a b =
  if a == 0
    then putStrLn(show(b))
  else do
    let c = a `mod` 10
    sborDelenie (quot a 10) (b+c)

main = do
  input <- getLine
  let x = (read input :: Int)
  let sbor = 0
  sborDelenie x sbor