#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n;
  cin >> n;
  long long int k = 7 + 3 * (n - 1);
  cout << k << "\n";
  long long int x = 1, y = 1, z = 1;
  for (long long int i = 0; i < n + 2; i++) {
    cout << i << " " << i << "\n";
  }
  for (long long int i = 0; i < n + 1; i++) {
    cout << i << " " << i + 1 << "\n";
  }
  for (long long int i = 0; i < n + 1; i++) {
    cout << i + 1 << " " << i << "\n";
  }
}
