#include <iostream>
#include <fstream>
#include <utility>
#include <algorithm>
#include <iomanip>

using namespace std;

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

typedef pair < double, double > Point;

const int NMax = 120005;

int n,head;
Point v[NMax],stak[NMax];

inline double cross_product(const Point &A, const Point &B, const Point &C){
    return (B.first - A.first) * (C.second - A.second) - (B.second - A.second) * (C.first - A.first);
}

inline bool cmp(const Point &p1, const Point &p2){
    return cross_product(v[1], p1, p2) < 0;
}

inline void swep(Point &a, Point &b){
    Point aux = a;
    a = b;
    b = aux;
}

void sort_points(){
    int pos = 1;
    for(int i = 2; i <= n; i++){
        if(v[i] < v[pos]){
            pos = i;
        }
    }
    swep(v[1],v[pos]);
    sort(v + 2, v + n + 1, cmp);
}

void convex_hull(){
    sort_points();
    stak[1] = v[1];
    stak[2] = v[2];
    head = 2;
    for(int i = 3; i <= n; i++){
        while(head >= 2 && cross_product(stak[head - 1], stak[head], v[i]) > 0){
            head--;
        }
        stak[++head] = v[i];
    }
}

int main()
{
    fin >> n;
    for(int i = 1; i <= n; i++){
        fin >> v[i].first >> v[i].second;
    }
    convex_hull();
    fout << fixed;
    fout << head << "\n";
    for(int i = head; i > 0; i--){
        fout << setprecision(9) << stak[i].first << " " << stak[i].second << "\n";
    }
    return 0;
}