import java.util.*;
 
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  }
} import java.util.*; util.* java public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc while(n > 1000){
      n = n - 1000;
  } n > 1000 n 1000 {
      n = n - 1000;
  } n = n - 1000 n n - 1000 n 1000 int ans = 1000 - n; ans 1000 - n 1000 n System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  }
} public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  }
} Main
import java.util.*;
 
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    while(n > 1000){
      n = n - 1000;
  }
    int ans = 1000 - n;
    System.out.println(ans);
  }
}