#include <bits/stdc++.h>
using namespace std;
const long long maxn = 300010;
const long long MOD = 1e9 + 7;
const long long MOD2 = 998244353;
const long long INF = 1e9;
const long long LINF = 1e18;
long long n, m, a[maxn], b[maxn];
map<long long, long long> M, N;
string s, ss;
set<long long> S;
void solve() {
  cin >> n;
  vector<pair<long long, long long> > v;
  for (long long i = 0; i <= n; i++) {
    v.push_back({i, i});
    v.push_back({i + 1, i});
    v.push_back({i, i + 1});
  }
  v.push_back({n + 1, n + 1});
  cout << v.size() << "\n";
  for (auto u : v) cout << u.first << " " << u.second << "\n";
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  ;
  long long t = 1;
  while (t--) solve();
}
