#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j;
  cin >> n;
  cout << (3 * n) + 4 << endl;
  cout << 0 << " " << 0 << endl;
  cout << 0 << " " << 1 << endl;
  for (i = 1; i <= n; i++) {
    for (j = i - 1; j <= i + 1; j++) cout << i << " " << j << endl;
  }
  cout << n + 1 << " " << n << endl;
  cout << n + 1 << " " << n + 1 << endl;
  return 0;
}
