#include <algorithm>
#include <iostream>
#include <fstream>
#include <climits>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>

#include <iomanip>
#include <cassert>

#include <random>
#include <chrono>

// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using ull = unsigned long long;
//using ll = long long;

//#define int __int128
//#define int ll
#define pii pair <int, int>
#define all(a) (a).begin(), (a).end()
#define fr first
#define sc second
#define pb push_back
#define lb lower_bound
#define ub upper_bound

#define vt vector
#define FOR(a, b) for(int i = (a); i <= (b); i++)
#define FORr(a, b) for(int i = (a); i >= (b); i--)
#define sz(x) (int)(x).size()

#define YES cout << "YES\n"
#define NO cout << "NO\n"

using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int rangerng(int l, int r){
    return uniform_int_distribution<>(l, r)(rng);
}

string filename = "infasuratoare";
ifstream fin(filename + ".in");
ofstream fout(filename + ".out");

////////////////////////////////////////////////////////////////////////////////////

const int NMAX = 12e4;

struct Point{
    double x, y;
}v[NMAX + 1];

double A(Point p1, Point p2, Point p3){
    return p1.x * (p2.y - p3.y) + p2.x * (p3.y - p1.y) + p3.x * (p1.y - p2.y);
}

bool cmp(Point a, Point b){
    if(a.x == b.x){
        return a.y < b.y;
    }
    return a.x < b.x;
}

void solve(){
    int n;
    fin >> n;

    for(int i = 1; i <= n; i++){
        fin >> v[i].x >> v[i].y;
    }

    sort(v + 1, v + n + 1, cmp);

    vt <int> up;
    vt <int> down;

    for(int i = 1; i <= n; i++){
        while(sz(up) >= 2 && A(v[up[sz(up) - 2]], v[up[sz(up) - 1]], v[i]) <= 0){
            up.pop_back();
        }
        up.pb(i);

        while(sz(down) >= 2 && A(v[down[sz(down) - 2]], v[down[sz(down) - 1]], v[i]) >= 0){
            down.pop_back();
        }
        down.pb(i);
    }

    vt <int> ans = up;
    reverse(all(down));
    for(int i = 1; i + 1 < sz(down); i++){
        ans.pb(down[i]);
    }

    fout << sz(ans) << '\n';
    for(int ind : ans){
        fout << fixed << setprecision(12) << v[ind].x << ' ' << v[ind].y << '\n';
    }
}   


signed main(){

    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int T;
    //cin >> T;

    T = 1;

    while(T--){
        solve();
    }

    return 0;
}

/*
*/