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 CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
long long int greatestSubarraySum(long long int array[], long long int n);
long long int binarySearch(vector<long long> arr, long long int l,
                           long long int r, long long int x);
long long int modpower(long long int x, long long int y, long long int p);
long long int power(long long int x, long long int y);
long long int gcd(long long int a, long long int b);
long long int lcm(long long int a, long long int b);
long long int search(long long int arr[], long long int n, long long int k);
string findSum(string str1, string str2);
long long int extendedGcd(long long int a, long long int b, long long int &x,
                          long long int &y);
bool find_any_solution(long long int a, long long int b, long long int c,
                       long long int &x0, long long int &y0, long long int &g);
long long int countSetBits(long long int n);
void primeFactors(long long int n, map<long long int, long long int> &arr2,
                  long long int k, long long int &flaggy);
void matrixMultiply(long long int a[3][3], long long int b[3][3]);
void matrixPower(long long int first[7][7], long long int n);
long long int sumSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r);
vector<long long> squareRootDecompositionSumArray(long long int arr[],
                                                  long long int n);
long long int minSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r);
long long int maxSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r);
vector<long long> squareRootDecompositionMinArray(long long int arr[],
                                                  long long int n);
vector<long long> squareRootDecompositionMaxArray(long long int arr[],
                                                  long long int n);
void updateSquareRootDecompositionMinArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x);
void updateSquareRootDecompositionMaxArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x);
void updateSquareRootDecompositionSumArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x);
void dfs(long long int i, set<long long int> arr[], long long int visited[]);
void uni(long long int x, long long int y, long long int par[],
         long long int size[]);
long long int find(long long int x, long long int par[], long long int size[]);
long long int modulo(long long int value, long long int m);
class FenwickTree;
void pairsort(long long int a[], long long int b[], long long int n);
long long int max(long long int a, long long int b);
long long int min(long long int a, long long int b);
long long int modInverse(long long int a, long long int m);
long long int modsum(long long int a, long long int b, long long int m);
long long int modmul(long long int a, long long int b, long long int m);
string reverseOfString(string s);
long long int nCrMod(long long int n, long long int r, long long int mod);
vector<long long> kmpArray(string s);
long long int floorSqrt(long long int x);
long long int fact[1];
long long int sol(int a, int b, int n) {
  if (a < b) swap(a, b);
  if (a > n) return 0;
  return 1 + sol(b + a, a, n);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long int q = 1;
  for (long long int currentIndex = 0; currentIndex < q; currentIndex++) {
    long long int k;
    cin >> k;
    vector<pair<long long, long long> > v;
    v.push_back(make_pair(1, 0));
    int prev = 0;
    for (int i = 0; i < k / 2; i++) {
      v.push_back(make_pair(1, prev + 1));
      v.push_back(make_pair(1, prev + 2));
      v.push_back(make_pair(1, prev + 3));
      v.push_back(make_pair(0, prev + 2));
      v.push_back(make_pair(0, prev + 3));
      v.push_back(make_pair(2, prev + 2));
      v.push_back(make_pair(2, prev + 3));
      prev += 3;
    }
    v.push_back(make_pair(1, prev + 1));
    v.push_back(make_pair(1, prev + 2));
    prev += 2;
    v.push_back(make_pair(2, 0));
    v.push_back(make_pair(3, 0));
    v.push_back(make_pair(4, 0));
    v.push_back(make_pair(2, prev));
    v.push_back(make_pair(3, prev));
    v.push_back(make_pair(4, prev));
    for (int i = 1; i < prev; i++) {
      v.push_back(make_pair(4, i));
    }
    if (k % 2) {
      v.push_back(make_pair(0, prev));
      v.push_back(make_pair(0, prev + 1));
      v.push_back(make_pair(1, prev + 1));
    }
    cout << v.size() << endl;
    for (long long int i = 0; i < v.size(); i++)
      cout << v[i].first << " " << v[i].second << endl;
  }
  return 0;
}
vector<long long> kmpArray(string s) {
  vector<long long> arr(s.length(), 0);
  for (long long int i = 1; i < s.length(); i++) {
    long long int len = arr[i - 1];
    while (len > 0 && s[len] != s[i]) len = arr[len - 1];
    if (s[len] == s[i]) len++;
    arr[i] = len;
  }
  return arr;
}
long long int floorSqrt(long long int x) {
  if (x == 0 || x == 1) return x;
  long long int start = 1, end = x, ans;
  while (start <= end) {
    long long int mid = (start + end) / 2;
    if (mid * mid == x) return mid;
    if (mid * mid < x) {
      start = mid + 1;
      ans = mid;
    } else
      end = mid - 1;
  }
  return ans;
}
long long int nCrMod(long long int n, long long int r, long long int mod) {
  return (fact[n] * modInverse(fact[r], mod) % mod *
          modInverse(fact[n - r], mod) % mod) %
         mod;
}
void SieveOfEratosthenes(long long int n, bool isPrime[]) {
  isPrime[0] = isPrime[1] = false;
  for (long long int i = 2; i <= n; i++) isPrime[i] = true;
  for (long long int p = 2; p * p <= n; p++) {
    if (isPrime[p] == true) {
      for (long long int i = p * 2; i <= n; i += p) isPrime[i] = false;
    }
  }
}
string reverseOfString(string s) {
  string t;
  for (long long int i = 0; i < s.length(); i++) {
    t += s[s.length() - i - 1];
  }
  return t;
}
class FenwickTree {
 private:
  long long int n;
  long long int h(long long int i) { return (i | (i + 1)); }
  long long int g(long long int i) { return (i & (i + 1)); }

 public:
  long long int *sumtree;
  long long int *mainArray;
  FenwickTree(long long int n) {
    this->n = n;
    mainArray = (long long int *)malloc(n * sizeof(long long int));
    sumtree = (long long int *)calloc(n, sizeof(long long int));
  }
  void addElementAtIndex(long long int i, long long int x) {
    mainArray[i] = x;
    update(i, x);
  }
  void update(long long int i, long long int delta) {
    for (long long int j = i; j < n; j = h(j)) {
      sumtree[j] += delta;
    }
  }
  long long int sum(long long int i, long long int j) {
    long long int sum1 = 0, sum2 = 0;
    long long int i1 = i, j1 = j;
    while (j >= 0) {
      sum1 += sumtree[j];
      j = g(j) - 1;
    }
    while (i >= 0) {
      sum2 += sumtree[i];
      i = g(i) - 1;
    }
    return sum1 - sum2 + mainArray[i1];
  }
};
long long int modsum(long long int a, long long int b, long long int m) {
  return ((a % m) + (b % m)) % m;
}
long long int modmul(long long int a, long long int b, long long int m) {
  return ((a % m) * (b % m)) % m;
}
long long int modInverse(long long int a, long long int m) {
  return modpower(a, m - 2, m);
}
long long int max(long long int a, long long int b) {
  if (a > b)
    return a;
  else
    return b;
}
long long int min(long long int a, long long int b) {
  if (a < b) return a;
  return b;
}
void pairsort(long long int a[], long long int b[], long long int n) {
  pair<long long int, long long int> pairt[n];
  for (long long int i = 0; i < n; i++) {
    pairt[i].first = a[i];
    pairt[i].second = b[i];
  }
  sort(pairt, pairt + n);
  for (long long int i = 0; i < n; i++) {
    a[i] = pairt[i].first;
    b[i] = pairt[i].second;
  }
}
long long int extendedGcd(long long int a, long long int b, long long int &x,
                          long long int &y) {
  if (a == 0) {
    x = 0;
    y = 1;
    return b;
  }
  long long int x1, y1;
  long long int d = extendedGcd(b % a, a, x1, y1);
  x = y1 - (b / a) * x1;
  y = x1;
  return d;
}
bool find_any_solution(long long int a, long long int b, long long int c,
                       long long int &x0, long long int &y0, long long int &g) {
  g = extendedGcd(abs(a), abs(b), x0, y0);
  if (c % g) {
    return false;
  }
  x0 *= c / g;
  y0 *= c / g;
  if (a < 0) x0 = -x0;
  if (b < 0) y0 = -y0;
  return true;
}
string findSum(string str1, string str2) {
  if (str1.length() > str2.length()) {
    string s = str1;
    str1 = str2;
    str2 = s;
  }
  string str = "";
  int n1 = str1.length(), n2 = str2.length();
  reverse(str1.begin(), str1.end());
  reverse(str2.begin(), str2.end());
  int carry = 0;
  for (int i = 0; i < n1; i++) {
    int sum = ((str1[i] - '0') + (str2[i] - '0') + carry);
    str.push_back(sum % 10 + '0');
    carry = sum / 10;
  }
  for (int i = n1; i < n2; i++) {
    int sum = ((str2[i] - '0') + carry);
    str.push_back(sum % 10 + '0');
    carry = sum / 10;
  }
  if (carry) str.push_back(carry + '0');
  reverse(str.begin(), str.end());
  return str;
}
long long int binarySearch(vector<long long> arr, long long int l,
                           long long int r, long long int x) {
  if (r >= l) {
    long long int mid = l + (r - l) / 2;
    if (arr[mid] == x) return mid;
    if (arr[mid] > x) return binarySearch(arr, l, mid - 1, x);
    return binarySearch(arr, mid + 1, r, x);
  }
  return -1;
}
long long int greatestSubarraySum(long long int array[], long long int n) {
  long long int best = 0, sum = 0;
  for (long long int k = 0; k < n; k++) {
    sum = max(array[k], sum + array[k]);
    best = max(best, sum);
  }
  return best;
}
long long int modpower(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long int gcd(long long int a, long long int b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long int lcm(long long int a, long long int b) {
  return (a * b) / gcd(a, b);
}
long long int power(long long int x, long long int y) {
  long long int temp;
  if (y == 0) return 1;
  temp = power(x, y / 2);
  if (y % 2 == 0)
    return temp * temp;
  else
    return x * temp * temp;
}
long long int modulo(long long int value, long long int m) {
  long long int mod = value % m;
  if (value < 0) {
    mod += m;
  }
  return mod;
}
long long int find(long long int x, long long int par[], long long int size[]) {
  if (x == par[x])
    return x;
  else
    return par[x] = find(par[x], par, size);
}
void uni(long long int x, long long int y, long long int par[],
         long long int size[]) {
  x = find(x, par, size);
  y = find(y, par, size);
  if (size[x] > size[y]) swap(x, y);
  par[x] = y;
  size[y] += size[x];
}
void dfs(long long int i, set<long long int> arr[], long long int visited[]) {
  if (visited[i]) return;
  cout << (char)('a' + i);
  visited[i] = 1;
  for (auto u : arr[i]) dfs(u, arr, visited);
}
long long int countSetBits(long long int n) {
  long long int count = 0;
  while (n) {
    count += n & 1;
    n >>= 1;
  }
  return count;
}
long long int flag2;
void primeFactors(long long int n, map<long long int, long long int> &arr2,
                  long long int k, long long int &flaggy) {
  long long int count = 0;
  long long int flag = 0;
  while (n % 2 == 0) {
    n = n / 2;
    count++;
  }
  if (count % k != 0) {
    flag = 1;
    arr2[2] = count % k;
  }
  count = 0;
  for (int i = 3; i <= sqrt(n); i = i + 2) {
    while (n % i == 0) {
      n = n / i;
      count++;
    }
    if (count % k != 0) {
      flag = 1;
      arr2[i] = count % k;
    }
    count = 0;
  }
  if (n > 2) {
    if (1 % k != 0) {
      flag = 1;
      arr2[n] = 1 % k;
    }
  }
  if (flag == 0) {
    flag2++;
    flaggy = 1;
  }
}
void matrixMultiply(long long int *a[], long long int *b[], long long int n) {
  long long int mul[n][n];
  for (long long int i = 0; i < n; i++) {
    for (long long int j = 0; j < n; j++) {
      mul[i][j] = 0;
      for (long long int k = 0; k < n; k++) mul[i][j] += a[i][k] * b[k][j];
    }
  }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) a[i][j] = mul[i][j];
}
void matrixPower(long long int **first, long long int n, long long int k) {
  if (n == 1) return;
  long long int **M = (long long int **)malloc(k * sizeof(long long int *));
  for (long long int i = 0; i < k; i++) {
    M[i] = (long long int *)malloc(k * sizeof(long long int));
    for (long long int j = 0; j < k; j++) {
      M[i][j] = first[i][j];
    }
  }
  matrixPower(first, n / 2, k);
  matrixMultiply(first, first, k);
  if (n % 2 != 0) matrixMultiply(first, M, k);
}
vector<long long> squareRootDecompositionMinArray(long long int arr[],
                                                  long long int n) {
  long long int k = (long long int)ceil(sqrt(n));
  vector<long long> helper(k, std::numeric_limits<long long int>::max());
  for (long long int i = 0; i < n; i++)
    helper[i / k] = min(helper[i / k], arr[i]);
  return helper;
}
vector<long long> squareRootDecompositionMaxArray(long long int arr[],
                                                  long long int n) {
  long long int k = (long long int)ceil(sqrt(n));
  vector<long long> helper(k, -std::numeric_limits<long long int>::max());
  for (long long int i = 0; i < n; i++)
    helper[i / k] = max(helper[i / k], arr[i]);
  return helper;
}
long long int minSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r) {
  long long int k = (long long int)ceil(sqrt(n));
  long long int a = l / k;
  long long int b = r / k;
  long long int min1 = std::numeric_limits<long long int>::max();
  if (a == b) {
    for (long long int i = l; i < r + 1; i++) min1 = min(min1, arr[i]);
    return min1;
  }
  for (long long int i = l; i < (a + 1) * k; i++) min1 = min(min1, arr[i]);
  for (long long int i = a + 1; i < b; i++) min1 = min(min1, helper[i]);
  for (long long int i = b * k; i < r + 1; i++) min1 = min(min1, arr[i]);
  return min1;
}
long long int maxSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r) {
  long long int k = (long long int)ceil(sqrt(n));
  long long int a = l / k;
  long long int b = r / k;
  long long int min1 = -std::numeric_limits<long long int>::max();
  if (a == b) {
    for (long long int i = l; i < r + 1; i++) min1 = max(min1, arr[i]);
    return min1;
  }
  for (long long int i = l; i < (a + 1) * k; i++) min1 = max(min1, arr[i]);
  for (long long int i = a + 1; i < b; i++) min1 = max(min1, helper[i]);
  for (long long int i = b * k; i < r + 1; i++) min1 = max(min1, arr[i]);
  return min1;
}
vector<long long> squareRootDecompositionSumArray(long long int arr[],
                                                  long long int n) {
  long long int k = (long long int)ceil(sqrt(n));
  vector<long long> helper(k, 0);
  for (long long int i = 0; i < n; i++) helper[i / k] += arr[i];
  return helper;
}
void updateSquareRootDecompositionSumArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x) {
  long long int k = (long long int)ceil(sqrt(n));
  long long int delta = x - arr[i];
  arr[i] = x;
  helper[i / k] += delta;
}
void updateSquareRootDecompositionMinArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x) {
  long long int k = (long long int)ceil(sqrt(n));
  if (helper[i / k] == arr[i]) {
    if (x < arr[i])
      helper[i / k] = arr[i];
    else {
      long long int min1 = std::numeric_limits<long long int>::max();
      for (long long int j = i / k * k; j < (i / k + 1) * k; j++)
        min1 = min(min1, arr[j]);
      helper[i / k] = min1;
    }
  } else {
    helper[i / k] = min(helper[i / k], x);
  }
  arr[i] = x;
}
void updateSquareRootDecompositionMaxArray(long long int arr[],
                                           vector<long long> &helper,
                                           long long int n, long long int i,
                                           long long int x) {
  long long int k = (long long int)ceil(sqrt(n));
  if (helper[i / k] == arr[i]) {
    if (x < arr[i])
      helper[i / k] = arr[i];
    else {
      long long int min1 = -std::numeric_limits<long long int>::max();
      for (long long int j = i / k * k; j < (i / k + 1) * k; j++)
        min1 = max(min1, arr[j]);
      helper[i / k] = min1;
    }
  } else {
    helper[i / k] = max(helper[i / k], x);
  }
  arr[i] = x;
}
long long int sumSquareRootDecomposition(long long int arr[],
                                         vector<long long> helper,
                                         long long int n, long long int l,
                                         long long int r) {
  long long int k = (long long int)ceil(sqrt(n));
  long long int a = l / k;
  long long int b = r / k;
  long long int sum = 0;
  if (a == b) {
    for (long long int i = l; i < r + 1; i++) sum += arr[i];
    return sum;
  }
  for (long long int i = l; i < (a + 1) * k; i++) {
    sum += arr[i];
  }
  for (long long int i = b * k; i < r + 1; i++) sum += arr[i];
  for (long long int i = a + 1; i < b; i++) sum += helper[i];
  return sum;
}