#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  int n;
  cin >> n;
  cout << 7 + ((n - 1) * 3) << "\n";
  cout << "0"
       << " "
       << "0"
       << "\n";
  for (int i = 1; i <= n + 1; i++) {
    cout << i << " " << i << "\n";
    cout << i << " " << i - 1 << "\n";
    cout << i - 1 << " " << i << "\n";
  }
  return 0;
}
