#include <bits/stdc++.h>
using namespace std;
void flash() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
long long pw(long long x, long long y) {
  if (y == 0) return 1;
  if (y == 1) return x;
  long long ans = pw(x, y / 2);
  ans = ans * ans;
  if (y % 2 == 1) ans = ans * x;
  return ans;
}
long long pwm(long long x, long long y) {
  if (y == 0) return 1;
  if (y == 1) return x;
  long long ans = pwm(x, y / 2) % 998244353;
  ans = (ans * ans) % 998244353;
  if (y % 2 == 1) ans = (ans * x) % 998244353;
  return ans;
}
long long check(long long n) {
  if (n < 0)
    return 0;
  else
    return 1;
}
long long add(long long a, long long b) { return a + b; }
long long max(long long a, long long b) {
  if (a > b)
    return a;
  else
    return b;
}
long long min(long long a, long long b) {
  if (a > b)
    return b;
  else
    return a;
}
long long minv(long long a, long long m) {
  long long m0 = m;
  long long y = 0, x = 1;
  if (m == 1) return 0;
  while (a > 1) {
    long long q = a / m, t = m;
    m = a % m, a = t, t = y;
    y = x - q * y;
    x = t;
  }
  if (x < 0) x += m0;
  return x;
}
bool cmp(long long i1, long long i2) { return (i1 > i2); }
void solve() {
  long long n;
  cin >> n;
  vector<array<long long, 2>> v;
  v.push_back({0, 0});
  v.push_back({0, 1});
  long long x = 1, y = 0;
  for (long long i = 0; i < n; i++) {
    long long z = y;
    for (long long j = 0; j < 3; j++) {
      v.push_back({x, z});
      z++;
    }
    x++;
    y++;
  }
  v.push_back({x, y});
  v.push_back({x, y + 1});
  cout << (long long)v.size() << "\n";
  for (long long i = 0; i < (long long)v.size(); i++) {
    cout << v[i][0] << " " << v[i][1] << "\n";
  }
}
int32_t main() {
  flash();
  long long t;
  t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
