#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  int ans, x, y = 1;
  ans = (n + 1) * 3 + 1;
  cout << ans << "\n";
  for (x = 0; x <= n + 1; x++) {
    for (y = x - 1; y <= x + 1; y++) {
      if (y < 0)
        continue;
      else if (x == n + 1 && y == x + 1)
        break;
      else
        cout << x << " " << y << "\n";
    }
  }
  return 0;
}
