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

public class Main {

  public static void main(String[] args) {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  }

} import java.util.*; util.* java import java.io.*; io.* java public class Main {

  public static void main(String[] args) {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  }

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

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  } main {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  } Scanner in = new Scanner(System.in); in new Scanner(System.in) int N = in.nextInt(); N in.nextInt() in.nextInt in int bill = 1000; bill 1000 if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      } N%bill==0 N%bill N bill 0 {


          System.out.println(0);
      } System.out.println(0) System.out.println System.out System System.out 0 {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      } int no_of_notes = N/bill + 1; no_of_notes N/bill + 1 N/bill N bill 1 System.out.println(no_of_notes*1000-N) System.out.println System.out System System.out no_of_notes*1000-N no_of_notes*1000 no_of_notes 1000 N String[] args args public class Main {

  public static void main(String[] args) {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  }

} public class Main {

  public static void main(String[] args) {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  }

} Main

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

public class Main {

  public static void main(String[] args) {

      Scanner in = new Scanner(System.in);
      int N = in.nextInt();
      int bill = 1000;

      if(N%bill==0)
      {


          System.out.println(0);
      }
        else
      {
          int no_of_notes = N/bill + 1;
          System.out.println(no_of_notes*1000-N);
      }
  }

}
