#include <bits/stdc++.h>
using namespace std;
long long mod = 1000000007;
const long long inf = 92233720368547758;
bool isprime(long long n) {
  for (int i = 2; i * i <= n; i++)
    if (n % i == 0) return 0;
  return 1;
}
long long fpow(long long a, long long b) {
  return b ? fpow(a * a % mod, b / 2) * (b % 2 ? a : 1) % mod : 1;
}
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long inv(long long i) {
  if (i == 1) return 1;
  return (mod - ((mod / i) * inv(mod % i)) % mod) % mod;
}
long long dtb(long long x) {
  long long ans = 0;
  long long y = 1;
  while (x > 0) {
    ans += (x % 2) * y;
    x = x / 2;
    y = y * 10;
  }
  return ans;
}
vector<long long> adj[100009], vis(100009, 0), adjr[100009], c[100009];
long long arr[100009];
long long cnt = 0;
bool comp(long long x, long long y) { return arr[x] < arr[y]; }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long T = 1;
  long long n, m, k, w;
  string s, s1, s2;
  string srr[100009];
  long long a, b, x, y, z, l, r, t, p, d;
  long long ans = 0, sum = 0, pos = 0;
  long long mx = 0, mn = 1000000000;
  vector<long long> va(500009, 0), vb(500009, 0), vc(500009, 0);
  map<long long, long long> make_pair;
  vector<long long> v, v1;
  vector<pair<long long, long long>> v2;
  while (T--) {
    cin >> n;
    cout << 3 * n + 4 << "\n";
    cout << "0 0"
         << "\n";
    cout << "0 1"
         << "\n";
    for (int i = 1; i <= n; i++) {
      cout << i << " " << i - 1 << "\n";
      cout << i << " " << i << "\n";
      cout << i << " " << i + 1 << "\n";
    }
    cout << n + 1 << " " << n << "\n";
    cout << n + 1 << " " << n + 1 << "\n";
  }
  return 0;
}
