import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author HussienMoustafa
 */
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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}
 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.StringTokenizer; StringTokenizer java.util import java.io.IOException; IOException java.io import java.io.BufferedReader; BufferedReader java.io import java.io.InputStreamReader; InputStreamReader java.io import java.io.InputStream; InputStream java.io 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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
} 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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    } APayment public void solve(int testNumber, Scanner s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        } solve {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        } int n = s.nextInt() n s.nextInt() s.nextInt s sum = 1000; sum 1000 while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            } true {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            } if (sum >= n) {
                    sout.println(sum - n);
                    break;
                } sum >= n sum n {
                    sout.println(sum - n);
                    break;
                } sout.println(sum - n) sout.println sout sum - n sum n break; sum += 1000 sum 1000 int testNumber testNumber Scanner s s PrintWriter sout sout static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    } Scanner StringTokenizer st; st BufferedReader br; br public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        } Scanner {
            br = new BufferedReader(new InputStreamReader(s));
        } br = new BufferedReader(new InputStreamReader(s)) br new BufferedReader(new InputStreamReader(s)) InputStream s s public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        } next {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        } while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            } st == null || !st.hasMoreTokens() st == null st null !st.hasMoreTokens() st.hasMoreTokens() st.hasMoreTokens st {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            } try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                } catch (IOException e) {
                    throw new RuntimeException(e);
                } IOException e {
                    throw new RuntimeException(e);
                } throw new RuntimeException(e); new RuntimeException(e) {
                    st = new StringTokenizer(br.readLine());
                } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st public int nextInt() {
            return Integer.parseInt(next());
        } nextInt {
            return Integer.parseInt(next());
        } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next 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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
} 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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author HussienMoustafa
 */
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 s, PrintWriter sout) {
            int n = s.nextInt(), sum = 1000;

            while (true) {
                if (sum >= n) {
                    sout.println(sum - n);
                    break;
                }
                sum += 1000;
            }
        }

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}

