// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}

double cross(const Pd &o, const Pd &a, const Pd &b){
  return (a.first - o.first) * (b.second - o.second) - (a.second - o.second) * (b.first - o.first);
}

vector<Pd> convex_hull(vector<Pd> vec){
  int n = vec.size(), k = 0;
  if(n < 3)return vec;

  vector<Pd> ch(2 * n);
  sort(vec.begin(), vec.end());

  // lower
  for(int i = 0; i < n; i++){
    while(k >= 2 && cross(ch[k-2], ch[k-1], vec[i]) < 0.)k--;
    ch[k++] = vec[i];
  }

  // upper
  for(int i = n - 1, t = k + 1; i > 0; --i){
    while(k >= t && cross(ch[k-2], ch[k-1], vec[i-1]) < 0.)k--;
    ch[k++] = vec[i-1];
  }

  ch.resize(k - 1);
  return ch;

}

bool comp(const Pd &a, const Pd &b){
  if(a.SE != b.SE)return a.SE < b.SE;
  return a.FI < b.FI;
}

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<Pd> vec(n);
  rep(i, n){
    cin >> vec[i].FI >> vec[i].SE;
  }
  auto v = convex_hull(vec);
  auto vv = v;
  sort(all(vv), comp);
  int i = 0;
  for(; i < sz(v); i++)if(v[i] == vv[0])break;
  cout << sz(v) << endl;
  FOR(j, i, sz(v))cout << v[j].FI << " " << v[j].SE << endl;
  rep(j, i)cout << v[j].FI << " " << v[j].SE << endl;
	return 0;
}

