#include <bits/stdc++.h>
using namespace std;
void solve() {
  long long n;
  cin >> n;
  vector<pair<long long, long long>> ans;
  long long i = 0;
  long long j = 0;
  ans.push_back({0, -1});
  ans.push_back({-1, 0});
  ans.push_back({-1, -1});
  for (long long k = 0; k < n; k++) {
    ans.push_back({i, j});
    ans.push_back({i, j + 1});
    ans.push_back({i + 1, j});
    i++;
    j++;
  }
  ans.push_back({i, j});
  cout << ans.size() << endl;
  for (long long i = 0; i < ans.size(); i++)
    cout << ans[i].first << " " << ans[i].second << endl;
}
signed main() {
  long long t;
  t = 1;
  while (t--) {
    solve();
  }
}
