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