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

using namespace std;

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

const int DIM = 120005;

int n,head=1;

struct Pair
{
    double x,y;
};

Pair v[DIM],Stack[DIM];

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

double Check(Pair a, Pair b, Pair c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}

bool Compare(Pair a, Pair b)
{
    return Check(v[1],a,b)<0;
}

void Sort()
{
    int xMin=0,yMin=0,pos=1;
    xMin=v[1].x;
    yMin=v[2].y;
    for(int i=2;i<=n;i++)
    {
        if(v[i].x<xMin)
        {
            xMin=v[i].x;
            yMin=v[i].y;
            pos=i;
        }
        else if(v[i].x==xMin)
        {
            if(v[i].y<yMin)
            {
                yMin=v[i].y;
                pos=i;
            }
        }
    }
    swap(v[1],v[pos]);
    sort(v+2,v+1+n,Compare);
}

void Convex()
{
    Sort();
    Stack[1]=v[1];
    Stack[2]=v[2];
    head=2;
    for(int i=3;i<=n;i++)
    {
        while(head>=2 && Check(Stack[head-1],Stack[head],v[i])>0)
            head--;
        head++;
        Stack[head]=v[i];
    }
}

void Show()
{
    fout<<head<<'\n';
    for(int i=head;i>=1;i--)
        fout<<fixed<<setprecision(9)<<Stack[i].x<<" "<<Stack[i].y<<'\n';
}

int main()
{
    Read();
    Convex();
    Show();
}