import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    }
} import java.io.*; io.* java import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    }
} Main public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0); N%1000 != 0 N%1000 N 1000 0 System.out.println((N/1000 + 1)*1000 - N) System.out.println System.out System System.out (N/1000 + 1)*1000 - N (N/1000 + 1)*1000 (N/1000 + 1) N/1000 N 1000 1 1000 N System.out.println(0) System.out.println System.out System System.out 0 String[] args args public class Main {
    public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    }
} public class Main {
    public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    }
} Main
import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException
    {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        if(N%1000 != 0)
            System.out.println((N/1000 + 1)*1000 - N);
        else
            System.out.println(0);
    }
}