import java.util.*;

public class Main{
    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    }
} import java.util.*; util.* java public class Main{
    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    }
} Main public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    } main {

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int N = scanner.nextInt(); N scanner.nextInt() scanner.nextInt scanner int minN = 1; minN 1 int maxN = 10000; maxN 10000 if(N < minN || N > maxN ){
            return;
        } N < minN || N > maxN N < minN N minN N > maxN N maxN {
            return;
        } return; if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        } N % 1000 == 0 N % 1000 N 1000 0 {
            System.out.println(0);
        } System.out.println(0) System.out.println System.out System System.out 0 {
            System.out.println( 1000 - N % 1000 );
        } System.out.println( 1000 - N % 1000 ) System.out.println System.out System System.out 1000 - N % 1000 1000 N % 1000 N 1000 String[] args args public class Main{
    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    }
} public class Main{
    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    }
} Main
import java.util.*;

public class Main{
    public static void main(String[] args){

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();

        int minN = 1;
        int maxN = 10000;
        if(N < minN || N > maxN ){
            return;
        }

        if(N % 1000 == 0){
            System.out.println(0);
        }else{
            System.out.println( 1000 - N % 1000 );
        }
    }
}