#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;

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

#define nmax 120001

struct point
{
    double x,y;
} p[nmax];
int n,vf,vf2;
point stiva[nmax];
point stiva2[nmax];

bool cmp(point a, point b)
{
    if(a.x!=b.x) return a.x<b.x;
    else return a.y<b.y;
}

double cross_product(point o, point a, point b)
{
    a.x -= o.x;
    a.y -= o.y;
    b.x -= o.x;
    b.y -= o.y;
    return a.x * b.y - a.y * b.x;
}
int main()
{
    int i;
    fin>>n;
    for(i=0; i<n; ++i)
        fin>>p[i].x>>p[i].y;
    sort(p,p+n,cmp);
    stiva[++vf]=p[0];
    stiva[++vf]=p[1];

    for(i=2;i<n;++i)
    {
        while(vf>=2 && cross_product(stiva[vf-1],stiva[vf],p[i])<0) --vf;
        stiva[++vf]=p[i];
    }

    stiva2[++vf2]=p[n-1];
    stiva2[++vf2]=p[n-2];

    for(i=n-3;i>=0;--i)
    {
        while(vf2>=2 && cross_product(stiva2[vf2-1],stiva2[vf2],p[i])<0) --vf2;
        stiva2[++vf2]=p[i];
    }
    fout<<vf+vf2-2<<'\n';
    for(i=1;i<=vf;++i) fout<<fixed<<setprecision(6)<<stiva[i].x<<' '<<stiva[i].y<<'\n';
    for(i=2;i<vf2;++i) fout<<fixed<<setprecision(6)<<stiva2[i].x<<' '<<stiva2[i].y<<'\n';
}