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