import java.util.HashMap;
import java.util.Scanner;

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

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

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

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

} Main
import java.util.HashMap;
import java.util.Scanner;

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

}
