#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int64_t INF = INT64_MAX;
int32_t main() {
  long long n;
  cin >> n;
  vector<pair<long long, long long> > v = {{0, 0}, {0, 1}, {1, 0}, {1, 1}};
  long long x = 2, y = 2;
  while (n--) {
    v.push_back({x, y});
    v.push_back({x - 1, y});
    v.push_back({x, y - 1});
    x++, y++;
  }
  cout << v.size() << "\n";
  for (auto p : v) cout << p.first << " " << p.second << "\n";
  return 0;
}
