#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int tc = 1;
  while (tc--) {
    long long int n;
    cin >> n;
    int k = 2;
    vector<pair<int, int>> ans;
    ans.push_back({1, 1});
    ans.push_back({0, 0});
    ans.push_back({1, 0});
    ans.push_back({0, 1});
    for (int i = 0; i < n; i++) {
      ans.push_back({k, k});
      ans.push_back({k, k - 1});
      ans.push_back({k - 1, k});
      k++;
    }
    cout << ans.size() << "\n";
    for (int i = 0; i < ans.size(); i++) {
      cout << ans[i].first << " " << ans[i].second << "\n";
    }
  }
  return 0;
}
