#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 19, Mod = 1e9 + 7;
int n, m, q, A[N];
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n;
  vector<pair<int, int> > vec;
  int xc = 0, yc = 0;
  for (int i = 0; i <= n; i++) {
    int dif = (i % 2 == 0) ? (-1) : (1);
    for (int a = -1; a <= 1; a++)
      for (int b = -1; b <= 1; b++)
        if (a || b) vec.push_back({xc + a, yc + b + dif});
    xc += 2;
  }
  sort(vec.begin(), vec.end());
  vec.resize(unique(vec.begin(), vec.end()) - vec.begin());
  printf("%d\n", (int)vec.size());
  for (auto X : vec) printf("%d %d\n", X.first, X.second);
  return 0;
}
