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