#include <bits/stdc++.h>
using namespace std;
void solution() {
  long long n;
  cin >> n;
  long long centre = 1;
  long long left = n - 1;
  cout << 7 + left * (3) << endl;
  cout << centre + 1 << " " << 2 << endl << centre - 1 << " " << 0 << endl;
  std::cout << centre << " " << 1 << std::endl
            << centre - 1 << " " << 1 << endl
            << centre + 1 << " " << 1 << endl;
  cout << centre << " " << 0 << endl << centre << " " << 2 << endl;
  centre = 2;
  while (left--) {
    cout << centre + 1 << " " << centre << endl;
    cout << centre << " " << centre + 1 << endl;
    cout << centre + 1 << " " << centre + 1 << endl;
    centre++;
  }
}
int main() {
  solution();
  return 0;
}
