#include <bits/stdc++.h>
using namespace std;
int main() {
  int k;
  cin >> k;
  cout << 3 * k + 4 << endl;
  for (int i = 1; i <= k + 1; i++) {
    cout << k + 2 - i << ' ' << i << '\n' << k + 3 - i << ' ' << i << '\n';
    if (i == 1) {
    } else {
      cout << k + 4 - i << ' ' << i << '\n';
    }
  }
  cout << "1 " << k + 2 << endl << "2 " << k + 2 << endl;
}
