#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  cout << 3 * n + 4 << "\n0 0\n";
  for (int i = 0; i <= n; i++) {
    cout << i + 1 << " " << i << "\n";
    cout << i << " " << i + 1 << "\n";
    cout << i + 1 << " " << i + 1 << "\n";
  }
}
