import java.util.Scanner;

public class Main {
    public static void main(String[] var0) {
        Scanner scanner = new Scanner(System.in);

        int N = scanner.nextInt();
        int ans = 0;

        if (N < 1000) {
            ans = 1000 - N;
        } else if (N % 1000 == 0){
            System.out.println(0);
            System.exit(0);
        } else {
            String t = String.valueOf(N);
            char c = t.charAt(0);
            int thousand = Character.getNumericValue(c)*1000;
            ans = 1000 - (N - thousand);
        }

        System.out.println(ans);
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz