#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<pair<int, int>> vec;
  int greyx = 0;
  int greyy = 0;
  vec.push_back({greyx, greyy});
  vec.push_back({greyx + 1, greyy});
  vec.push_back({greyx + 1, greyy + 1});
  vec.push_back({greyx, greyy + 1});
  greyx++;
  greyy++;
  while (n--) {
    vec.push_back({greyx + 1, greyy});
    vec.push_back({greyx + 1, greyy + 1});
    vec.push_back({greyx, greyy + 1});
    greyx++;
    greyy++;
  }
  cout << vec.size() << endl;
  for (auto i : vec) {
    cout << i.first << " " << i.second << endl;
  }
  return 0;
}
