#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
vector<pair<int, int>> vp;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  vp.emplace_back(make_pair(0, 0));
  vp.emplace_back(make_pair(0 + 1, 0));
  vp.emplace_back(make_pair(0, 0 + 1));
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    vp.emplace_back(make_pair(i, i));
    vp.emplace_back(make_pair(i + 1, i));
    vp.emplace_back(make_pair(i, i + 1));
  }
  vp.emplace_back(make_pair(n + 1, n + 1));
  cout << vp.size() << '\n';
  for (int i = 0; i < vp.size(); i++) {
    cout << vp[i].first << ' ' << vp[i].second << '\n';
  }
  return 0;
}
