#include <bits/stdc++.h>
using namespace std;
const long long int inf = 1e18 + 1;
const long long int mod = 1e9 + 9;
int main() {
  long long int a, b, c, d, e, f, g, p, r, n, k, m, t, q, x, y;
  t = 1;
  string s1, s2, s3, s4, s5;
  for (int t0 = 1; t0 <= t; t0++) {
    cin >> n;
    cout << n * 3 + 4 << "\n";
    cout << "0 0\n1 0\n";
    for (int i = 1; i <= n; i++) {
      cout << i - 1 << " " << i << "\n";
      cout << i << " " << i << "\n";
      cout << i + 1 << " " << i << "\n";
    }
    n++;
    cout << n - 1 << " " << n << "\n";
    cout << n << " " << n << "\n";
  }
  return 0;
}
