//
//  main.cpp
//  Infasuratoare
//
//  Created by Albastroiu Radu on 10/26/16.
//  Copyright © 2016 Albastroiu Radu. All rights reserved.
//

#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
long long k,i,n,x,l,viz[100001];
struct sor
{
    double x,y;
}v[1200001],c[1200001];
int ecuatie(double x1,double x2,double x3,double y1,double y2,double y3)
{
    if((x3*y2+x2*y1+x1*y3)>(x1*y2+x2*y3+x3*y1))
        return 1;
    return 0;
}
int cmp(sor A,sor B)
{
    if(A.x==B.x)
        return A.y<B.y;
    else
        return A.x<B.x;
}
int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    c[1].x=v[1].x;c[1].y=v[1].y;k=1;
    for(i=2;i<=n;i++)
    {
        if(k==1)
            x=ecuatie(c[k].x,c[n].x,v[i].x,c[k].y,c[n].y,v[i].y);
        else
            x=ecuatie(c[k-1].x,c[k].x,v[i].x,c[k-1].y,c[k].y,v[i].y);
        if(x==1)
        {
            k++;
            c[k].x=v[i].x;
            c[k].y=v[i].y;
        }
        else
        {
            while(x==0)
            {
                if(k>1)
                    k--;
                else
                    break;
                x=ecuatie(c[k-1].x,c[k].x,v[i].x,c[k-1].y,c[k].y,v[i].y);
            }
            k++;
            c[k].x=v[i].x;
            c[k].y=v[i].y;
        }
    }
    l=k;
    for(i=n-1;i>0;i--)
    {
        x=ecuatie(c[k-1].x,c[k].x,v[i].x,c[k-1].y,c[k].y,v[i].y);
        if(x==1)
        {
            k++;
            c[k].x=v[i].x;
            c[k].y=v[i].y;
        }
        else
        {
            while(x==0)
            {
                if(k>l)
                    k--;
                else
                    break;
                x=ecuatie(c[k-1].x,c[k].x,v[i].x,c[k-1].y,c[k].y,v[i].y);
            }
            k++;
            c[k].x=v[i].x;
            c[k].y=v[i].y;
        }
    }
    fout<<k-1<<"\n";
    for(i=k;i>1;i--)
        fout<<setprecision(6)<<fixed<<c[i].x<<" "<<c[i].y<<"\n";
    return 0;
}