#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  cout << 7 + (3 * (k - 1)) << endl;
  cout << 1 << " " << 1 << endl;
  cout << 0 << " " << 1 << endl;
  cout << 0 << " " << 0 << endl;
  cout << 1 << " " << 0 << endl;
  cout << 2 << " " << 2 << endl;
  cout << 2 << " " << 1 << endl;
  cout << 1 << " " << 2 << endl;
  int i = 2;
  while (i <= k) {
    cout << i << " " << i + 1 << endl;
    cout << i + 1 << " " << i << endl;
    cout << i + 1 << " " << i + 1 << endl;
    i++;
  }
}
