#include <bits/stdc++.h>
using namespace std;
map<int, map<int, bool> > used;
int d[] = {1, -1, 0};
int main() {
  int n;
  cin >> n;
  int x = 10, y = 10;
  cout << 8 * (n + 1) - n << endl;
  for (int i = 1; i <= n + 1; i++) {
    for (int j = 0; j < 3; j++) {
      for (int k = 0; k < 3; k++) {
        if (!d[j] && !d[k]) continue;
        if (!used[x + d[j]][y + d[k]])
          cout << x + d[j] << " " << y + d[k] << endl;
        used[x + d[j]][y + d[k]] = 1;
      }
    }
    x += 2;
    y += 2;
  }
  return 0;
}
