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