#include <bits/stdc++.h>
using namespace std;
void input_array(vector<long long int> &A) {
  for (int i = 0; i < A.size(); i++) cin >> A[i];
}
int main() {
  long long int n, m, k, a, b, x, y, z, p;
  cin >> n;
  cout << 3 * n + 4 << endl;
  for (int i = 0; i < n + 2; i++) cout << i << " " << i << endl;
  for (int i = 0; i < n + 1; i++) {
    cout << i << " " << i + 1 << endl;
    cout << i + 1 << " " << i << endl;
  }
  return 0;
}
