#include <bits/stdc++.h>
  
using namespace std;
  
#if 1
    #define pv(x) cout<<#x<<" = "<<(x)<<"; ";cout.flush()
    #define pn cout<<endl
#else
    #define pv(x)
    #define pn
#endif
  
// #if 1
#ifdef INFOARENA
    ifstream in("infasuratoare.in");
    ofstream out("infasuratoare.out");
#else
    #define in cin
    #define out cout
#endif
  
using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
using ld = long double;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using pld = pair<ld, ld>;
using pdd = pair<double, double>;
#define pb push_back
const long double PI = 3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862;
const long double EPS = 1e-8;
const int inf_int = 1e9 + 5;
const ll inf_ll = 1e18 + 5;
const int NMax = 2e2 + 5;
const int mod = 1e9 + 7;
const int dx[] = {-1,0,0,+1}, dy[] = {0,-1,+1,0};
 
template<typename T>
T getOrientation(pair<T,T> a, pair<T,T> b, pair<T,T> c) {
    T ans = a.first * b.second + b.first * c.second + c.first * a.second;
    ans -= c.first * b.second + b.first * a.second + a.first * c.second;
    return ans;
}

template<typename T>
void andrewScan(vector<pair<T,T>> v, vector<pair<T,T>>& ans) {
    assert(v.size() > 2);
    ans.clear();
    
    sort(v.begin(), v.end());
    
    ans.pb(v[0]);
    ans.pb(v[1]);
    
    for (int i = 2; i < (int)v.size(); ++i) {
        T orient;
        int last = ans.size() - 1;
        while ( ans.size() >= 2 && (abs(orient = getOrientation(ans[last-1], ans[last], v[i])) < EPS || orient < 0) ) {
            ans.pop_back();
            last = ans.size() - 1;
        }
        ans.push_back(v[i]);
    }
    
    vector<pair<T,T>> up;
    up.pb(v[v.size() - 1]);
    up.pb(v[v.size() - 2]);    
    
    for (int i = v.size() - 3; i >= 0; --i) {
        T orient;
        int last = up.size() - 1;
        while ( up.size() >= 2 && (abs(orient = getOrientation(up[last-1], up[last], v[i])) < EPS || orient < 0) ) {
            up.pop_back();
            last = up.size() - 1;
        }
        up.push_back(v[i]);
    }
    
    for (int i = 1; i < (int)up.size() - 1; ++i) {
        ans.pb(up[i]);
    }
}
 
int main() {
    cin.sync_with_stdio(false);
    cin.tie(0);
    
    int N;
    in >> N;
    vector<pdd> v(N);
    for (auto& p : v) {
        in >> p.first >> p.second;    
    }
    
    vector<pdd> ans;
    andrewScan(v, ans);
    
    out << ans.size() << '\n';
    out << fixed << setprecision(13);
    for (auto& p : ans) {
        out << p.first << ' ' << p.second << '\n';
    }
    
    return 0;
}