import java.util.Scanner;
 
public class Main {
    public static void main(String[] args) {
        //N円の商品を1000円札のみで買い、お釣りを表示
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int money = 1000;
 
 
 
        if (N % money == 0) {//お釣りなし
            System.out.println(0);
        }else {//お釣りあり
            money = (N/money +1)*1000;
            System.out.println(money-N);
        }
    }
 
 
 
}
/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