Problem: Leo Jr. draws pictures in his notebook with checkered sheets (that is, each sheet has a regular square grid printed on it). We can assume that the sheets are infinitely large in any direction.

To draw a picture, Leo Jr. colors some of the cells on a sheet gray. He considers the resulting picture beautiful if the following conditions are satisfied:

  * The picture is connected, that is, it is possible to get from any gray cell to any other by following a chain of gray cells, with each pair of adjacent cells in the path being neighbours (that is, sharing a side).
  * Each gray cell has an even number of gray neighbours.
  * There are exactly n gray cells with all gray neighbours. The number of other gray cells can be arbitrary (but reasonable, so that they can all be listed).



Leo Jr. is now struggling to draw a beautiful picture with a particular choice of n. Help him, and provide any example of a beautiful picture.

To output cell coordinates in your answer, assume that the sheet is provided with a Cartesian coordinate system such that one of the cells is chosen to be the origin (0, 0), axes 0x and 0y are orthogonal and parallel to grid lines, and a unit step along any axis in any direction takes you to a neighbouring cell.

Input

The only line contains a single integer n (1 ≤ n ≤ 500) — the number of gray cells with all gray neighbours in a beautiful picture.

Output

In the first line, print a single integer k — the number of gray cells in your picture. For technical reasons, k should not exceed 5 ⋅ 10^5.

Each of the following k lines should contain two integers — coordinates of a gray cell in your picture. All listed cells should be distinct, and the picture should satisdfy all the properties listed above. All coordinates should not exceed 10^9 by absolute value.

One can show that there exists an answer satisfying all requirements with a small enough k.

Example

Input


4


Output


12
1 0
2 0
0 1
1 1
2 1
3 1
0 2
1 2
2 2
3 2
1 3
2 3

Note

The answer for the sample is pictured below:

<image>

Solution (in JAVA):

Solution:
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.ArrayList;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.InputStream;

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

    static class CChyotniiRisunok {
        int testNumber;
        InputReader in;
        OutputWriter out;

        public void solve() {
            int k = in.readInt();

            ArrayList<IntPt> res = new ArrayList<>();

            int j = 2;
            res.add(new IntPt(0, 0));
            res.add(new IntPt(0, 1));
            res.add(new IntPt(1, 0));
            res.add(new IntPt(1, 1));

            for (int i = 0; i < k; i++) {
                res.add(new IntPt(j, j));
                res.add(new IntPt(j, j - 1));
                res.add(new IntPt(j - 1, j));

                j++;
            }

            out.println(res.size());
            for (int i = 0; i < res.size(); i++) {
                out.println(res.get(i).x + " " + res.get(i).y);
            }

        }

        public void solve(int testNumber, InputReader in, OutputWriter out) {
            this.testNumber = testNumber;
            this.in = in;
            this.out = out;

            solve();
        }

    }

    static interface IPt<A, B> {
    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0) {
                    writer.print(' ');
                }
                writer.print(objects[i]);
            }
        }

        public void println(Object... objects) {
            print(objects);
            writer.println();
        }

        public void close() {
            writer.close();
        }

        public void println(int i) {
            writer.println(i);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class IntPt implements Comparable<IntPt>, IPt<Integer, Integer> {
        public final int x;
        public final int y;

        public IntPt(int k, int v) {
            x = k;
            y = v;
        }

        public IntPt(IntPt entry) {
            this(entry.getX(), entry.getY());
        }

        public Integer getX() {
            return x;
        }

        public Integer getY() {
            return y;
        }

        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof IntPt)) {
                return false;
            } else {
                return x == ((IntPt) o).x && y == ((IntPt) o).y;
            }
        }

        public int hashCode() {
            int result = Integer.hashCode(x);

            final int h = Integer.hashCode(y);
            result = 37 * result + h ^ (h >>> 16);

            return result;
        }

        public String toString() {
            return "[" + getX() + ", " + getY() + "]";
        }

        public int compareTo(IntPt o) {
            if (x == o.x) {
                return Integer.compare(y, o.y);
            }
            return Integer.compare(x, o.x);
        }

    }
}