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.*;
import java.util.*;
public class P1368C {
    static InputReader in = new InputReader(System.in);
    static PrintWriter pw = new PrintWriter(System.out);
    static long mod = (long) (Math.pow(10, 9)) + 7;
    static HashMap<Integer, List<Integer>> adjList = new HashMap<>();
    static boolean[] visited;
    public static void main(String[] args) {
//        int test = in.nextInt();
        int test = 1;
        while(test-->0) {
            solve();
        }
        pw.close();
    }

    static void solve() {
        int n = in.nextInt();
        int k = 4;
        k += (3 * n);
        pw.println(k);

        pw.println("0 0");
        pw.println("0 1");
        pw.println("1 0");
        pw.println("1 1");

        // Print n triple corners.
        for (int row = 2; row <= n+1; row++) {
            pw.println(row + " " + row);
            pw.println((row - 1) + " " + row);
            pw.println(row + " " + (row - 1));
        }
    }

    static long fast_pow(long a, long b) {
        if(b == 0)
            return 1L;

        long val = fast_pow(a, b / 2);

        if(b % 2 == 0)
            return val * val % mod;
        else
            return val * val % mod * a % mod;
    }

    static void sort(long[] a) //check for long
    {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class UF {
        // Number of connected components
        private int count;
        // Store a tree
        private int[] parent;
        // Record the "weight" of the tree
        private int[] size;

        public UF(int n) {
            this.count = n;
            parent = new int[n];
            size = new int[n];
            for (int i = 0; i < n; i++) {
                parent[i] = i;
                size[i] = 1;
            }
        }

        public void union(int p, int q) {
            int rootP = find(p);
            int rootQ = find(q);
            if (rootP == rootQ)
                return;

            // The small tree is more balanced under the big tree
            if (size[rootP] > size[rootQ]) {
                parent[rootQ] = rootP;
                size[rootP] += size[rootQ];
            } else {
                parent[rootP] = rootQ;
                size[rootQ] += size[rootP];
            }
            count--;
        }

        public boolean connected(int p, int q) {
            int rootP = find(p);
            int rootQ = find(q);
            return rootP == rootQ;
        }

        private int find(int x) {
            while (parent[x] != x) {
                // Path compression
                parent[x] = parent[parent[x]];
                x = parent[x];
            }
            return x;
        }

        public int count() {
            return count;
        }
    }
    static class InputReader {

        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;

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

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

        public int nextInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public long nextLong() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public int[] nextIntArray(int n) {
            int [] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }
        public long[] nextLongArray(int n) {
            long [] a = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextLong();
            }
            return a;
        }

        public static int[] shuffle(int[] a, Random gen)
        { for(int i = 0, n = a.length;i < n;i++)
        { int ind = gen.nextInt(n-i)+i;
            int d = a[i];
            a[i] = a[ind];
            a[ind] = d;

        }
            return a;
        }


        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        }

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

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        }
    }
}