#include <bits/stdc++.h>
int dx4[] = {0, 0, -1, 1};
int dy4[] = {-1, 1, 0, 0};
bool valid(int r, int c, int x, int y) {
  if (x >= 1 && x <= r && y >= 1 && y <= c) return 1;
  return 0;
}
using namespace std;
int main() {
  int n;
  cin >> n;
  cout << (3 * n + 4) << endl;
  cout << "0 0" << endl;
  cout << "0 1" << endl;
  for (int i = 1; i <= n; i++) {
    for (int j = (i - 1); j <= (i + 1); j++) cout << i << " " << j << endl;
  }
  cout << n + 1 << " " << n << endl;
  cout << n + 1 << " " << n + 1 << endl;
  return 0;
}
