#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
#include <iomanip>
#include <algorithm>
#include <deque>
//#include <bits/stdc++.h>
#define in fin
#define out fout

using namespace std;
using db = long double;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct punct{
    db x, y, rad; // radiani
};

db det(punct a, punct b, punct c){
    a.x -= c.x;
    b.x -= c.x;
    a.y -= c.y;
    b.y -= c.y;
    return a.x * b.y - a.y * b.x;
}

bool cmp(punct a, punct b){
    if(a.rad != b.rad) return a.rad > b.rad;
    else if(a.x != b.x) return a.x > b.x;
    else return a.y > b.y;
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n; in >> n;
    punct v[n];
    db x0 = 0, y0 = 0;

    for(int i = 0; i < n; i++){
        in >> v[i].x >> v[i].y;
        x0 += v[i].x;
        y0 += v[i].y;
    }

    x0 /= n;
    y0 /= n;

    // cout << "x0 = " << x0 << " y0 = " << y0 << '\n';

    for(int i = 0; i < n; i++){
        v[i].rad = atan2(v[i].y - y0, v[i].x - x0);
        // cout << "i = " << i << " v = " << v[i].x << " " << v[i].y << " rad = " << v[i].rad << '\n';
    }

    sort(v + 0, v + n, cmp);

    // cout << "v : \n";
    // for(int i = 0; i < n; i++){
    //     cout << v[i].x << " " << v[i].y << '\n';
    // }

    deque< punct > sol;
    for(int i = 0; i < n; i++){
        // cout << "Suntem la ( " << v[i].x << " , " << v[i].y << " )\n";
        while(sol.size() >= 2){
            punct a = sol[ sol.size() - 2 ];
            punct b = sol[ sol.size() - 1 ];

            if( det( a, b, v[i] ) > 0 ){
                // cout << " -- > Eliminam " << b.x << " , " << b.y << '\n';
                sol.pop_back();
            }else break;
        }
        sol.push_back(v[i]);
    }
    // out << sol.size() << '\n';
    // for(int i = 0; i < sol.size(); i++){
    //     out << fixed << setprecision(6) << sol[i].x << " " << sol[i].y << '\n';
    // }

    while(sol.size() >= 3){
        punct a = sol[ sol.size() - 2 ];
        punct b = sol[ sol.size() - 1 ];

        if( det( sol[0], a, b ) > 0 ){
            sol.pop_back();
        }else break;
    }

    while(sol.size() >= 3){
        punct a = sol[ sol.size() - 1 ];
        punct b = sol[ 0 ];

        if( det( sol[0], sol[1], sol[sol.size() - 1] ) > 0 ){
            sol.pop_front();
        }else break;
    }

    reverse(sol.begin(), sol.end());

    out << sol.size() << '\n';
    for(int i = 0; i < sol.size(); i++){
        out << fixed << setprecision(12) << sol[i].x << " " << sol[i].y << '\n';
    }
    
    return 0;
}