import java.util.*;
public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  }
} import java.util.*; util.* java public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  }
} Main public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }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 int a = n%1000; a n%1000 n 1000 int b = 1000-a; b 1000-a 1000 a if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    } b != 1000 b 1000 {
      System.out.println(b);
    } System.out.println(b) System.out.println System.out System System.out b {
      System.out.println(0);
    } 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){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  }
} public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  }
} Main
import java.util.*;
public class Main {
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    
    int a = n%1000;
    
    int b = 1000-a;
    
    if(b != 1000){
      System.out.println(b);
    }else{
      System.out.println(0);
    }
  
  }
}