#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  vector<pair<long long, long long> > ans;
  long long n;
  cin >> n;
  long long x = 0;
  for (long long i = 0; i <= n; i++, x++) {
    ans.push_back({x, x});
    ans.push_back({x, x + 1});
    ans.push_back({x + 1, x});
  }
  ans.push_back({x, x});
  cout << ans.size() << endl;
  for (auto x : ans) cout << x.first << " " << x.second << endl;
  return 0;
}
