{-# LANGUAGE PartialTypeSignatures #-}
module Main (main) where

import qualified Data.ByteString.Char8 as C8
import qualified Data.Char as C
import qualified Data.List as L

main :: IO ()
main = readInts >>= output . solve

solve :: [Int] -> Int
solve [n] = if r == 0 then 0 else 1000 - r
  where
    r = n `mod` 1000

output :: Int -> IO ()
output = print

-- utils
readInts :: IO [Int]
readInts = L.unfoldr (C8.readInt . C8.dropWhile C.isSpace) <$> C8.getLine