#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<pair<int, int>> v;
  int x = 0, y = 0;
  for (int i = 0; i <= n; i++) {
    v.push_back({x, y});
    v.push_back({x + 1, y});
    v.push_back({x, y + 1});
    x++;
    y++;
  }
  v.push_back({x, y});
  cout << v.size() << "\n";
  for (int i = 0; i < v.size(); i++) {
    cout << v[i].first << " " << v[i].second << "\n";
  }
  return 0;
}
