#include <bits/stdc++.h>
long long int power(long long int x, long long int b) {
  long long int p = 1;
  while (b > 0) {
    if (b & 1) {
      p = p * x;
      p %= 9000000000000000000;
    }
    b >>= 1;
    x *= x;
    x %= 9000000000000000000;
  }
  return p % 9000000000000000000;
}
using namespace std;
struct lex_compare {
  bool operator()(const pair<long double, long long int> p1,
                  const pair<long double, long long int> p2) {
    return (p1.first == p2.first) ? p1.second < p2.second : p1.first > p2.first;
  }
};
long double dist(long long int x, long long int y, long long int x1,
                 long long int y1) {
  return sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
}
bool compare(pair<long double, long double> p1,
             pair<long double, long double> p2) {
  return p1.first > p2.first;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  long long int n;
  cin >> n;
  long long int start = 0;
  vector<pair<long long int, long long int> > points;
  long long int i = 0;
  points.push_back({i, i + 1});
  points.push_back({i, i});
  for (i = 1; i < n + 1; i++) {
    points.push_back({i, i + 1});
    points.push_back({i, i});
    points.push_back({i, i - 1});
  }
  points.push_back({i, i - 1});
  points.push_back({i, i});
  cout << points.size() << "\n";
  for (auto i : points) {
    cout << i.first << " " << i.second << "\n";
  }
  return 0;
}
