//package hiougyf;
import java.util.*;

public class Main {

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

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

public class Main {

	public static void main(String[] args) {
		 Scanner sc =new Scanner(System.in);
	int t=sc.nextInt();
	 int a=t%1000;
	 if(a!=0)System.out.println(1000-a);
	 else System.out.println("0");		
	}
	
}
	