#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <fstream>
#define NMAX 120005
using namespace std;

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

vector < pair < double , double > > points;
pair < double , double > st[NMAX];
int N, top;

double crossProduct(pair <double,double> A,pair <double,double> B,pair <double,double> C)
{
    return (B.first - A.first) * (C.second - A.second) - (B.second - A.second) * (C.first - A.first);
}

int CMP(pair <double,double> A, pair <double,double> B)
{
    return crossProduct(points[0],A,B) < 0;
}

void sortPoints()
{
    int pos = 0;
    for(int i = 1; i < points.size(); i++){
        if(points[pos] > points[i]){
            points[pos] = points[i];
        }
    }
    swap(points[0],points[pos]);
    sort(points.begin() + 1, points.end(),CMP);
}

void convexHull()
{
    top = 2;
    sortPoints();
    st[1] = points[0];
    st[2] = points[1];
    for(int i = 2; i < points.size(); i++){
        while(top >= 2 && crossProduct(st[top - 1],st[top],points[i]) > 0){
            top--;
        }
        st[++top] = points[i];
    }
}

int main()
{
    double x, y;
    fin >> N;
    for(int i = 1; i <= N; i++){
        fin >> x >> y;
        points.push_back(make_pair(x,y));
    }
    convexHull();
    fout << fixed;
    fout << top << "\n";
    for(int i = top; i >= 1; i--){
        fout << setprecision(9) << st[i].first << " " << st[i].second << "\n";
    }
    return 0;
}