#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  set<pair<long long, long long> > points;
  long long x = 1;
  long long y = 1;
  while (n--) {
    points.insert({x, y});
    points.insert({x - 1, y});
    points.insert({x + 1, y});
    points.insert({x, y - 1});
    points.insert({x, y + 1});
    points.insert({x - 1, y - 1});
    points.insert({x + 1, y + 1});
    x++;
    y++;
  }
  cout << points.size() << endl;
  for (auto p : points) cout << p.first << " " << p.second << endl;
  return 0;
}
