#include <bits/stdc++.h>
using namespace std;
using int64 = long long int;
template <class T>
vector<T> ReadArr(std::istream& in, int n) {
  vector<T> a(n);
  for (auto& it : a) in >> it;
  return a;
}
template <class T>
vector<vector<T>> BuildMat(int n, int m) {
  return vector<vector<T>>(n, vector<T>(m));
}
template <class T>
vector<vector<T>> ReadMat(std::istream& in, int n, int m) {
  auto a = BuildMat<T>(n, m);
  for (auto& row : a)
    for (auto& c : row) in >> c;
  return a;
}
class NumberIterator : std::iterator<std::forward_iterator_tag, int> {
 public:
  int v;
  int operator*() { return v; }
  NumberIterator(int v) : v(v) {}
  operator int&() { return v; }
};
class range : std::pair<int, int> {
 public:
  range(int begin, int end) : pair<int, int>(begin, std::max(begin, end)) {}
  range(int n) : pair<int, int>(0, std::max(0, n)) {}
  NumberIterator begin() { return first; }
  NumberIterator end() { return second; }
};
class CEvenPicture {
  void SolveOne(std::istream& in, std::ostream& out) {
    int n;
    in >> n;
    set<pair<int, int>> ans;
    int start = 0;
    vector<int> temp_x = {0, 1, 0, 1, 2, 1, 2};
    vector<int> temp_y = {0, 0, 1, 1, 1, 2, 2};
    for (int i = 0; i < n; i++) {
      if (i == 0) {
        for (int k = 0; k < temp_x.size(); k++) {
          ans.insert({start + temp_x[k], start + temp_y[k]});
        }
        start += 2;
      } else {
        for (auto j : range(2))
          for (auto k : range(2)) ans.insert({start + j, start + k});
        start++;
      }
    }
    out << ans.size() << endl;
    for (auto it : ans) {
      out << it.first << " " << it.second << endl;
    }
  }

 public:
  void solve(std::istream& in, std::ostream& out) {
    int TC = 1;
    while (TC--) {
      SolveOne(in, out);
    }
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  CEvenPicture solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}
