import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    }

    static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    }

    static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) APayment solver = new APayment(); solver new APayment() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    } APayment public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        } solve {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        } int n = in.nextInt(); n in.nextInt() in.nextInt in if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            } n % 1000 == 0 n % 1000 n 1000 0 {
                out.println("0");
            } out.println("0") out.println out "0" {
                int y = n % 1000;
                out.println(1000 - y);
            } int y = n % 1000; y n % 1000 n 1000 out.println(1000 - y) out.println out 1000 - y 1000 y int testNumber testNumber Scanner in in PrintWriter out out public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    }

    static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    }

    static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        APayment solver = new APayment();
        solver.solve(1, in, out);
        out.close();
    }

    static class APayment {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            int n = in.nextInt();
            if (n % 1000 == 0) {
                out.println("0");
            } else {
                int y = n % 1000;
                out.println(1000 - y);
            }
        }

    }
}

