#include <fstream>
#include <algorithm>
#include <cstdlib>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");;
ofstream fout("infasuratoare.out");
enum Orientare
{
    trig,
    orar,
    colin
};
struct pct
{
    double x, y;
};
Orientare calcOrientare(pct a, pct b, pct c)
{
    double det=(a.y-b.y)*(c.x-b.x)-(a.x-b.x)*(c.y-b.y);
    if(det>0)
        return trig;
    if(det<0)
        return orar;
    return colin;
}
bool fct_cst_srt(pct a, pct b)
{
    if(a.x<b.x)
        return true;
    if(a.x==b.x&&a.y<b.y)
        return true;
    return false;
}
int main()
{
    int n, k=2;
    pct a[120], sol[240];
    fin>>n;
    for(int i=0; i<n; i++)
        fin>>a[i].x>>a[i].y;
    sort(a, a+n, fct_cst_srt);
    sol[0].x=a[0].x, sol[0].y=a[0].y, sol[1].x=a[1].x, sol[1].y=a[1].y;
    for(int i=2; i<n; i++)
    {
        if(calcOrientare(sol[k-2], a[i], sol[k-1])==orar)
        {
            while(calcOrientare(sol[k-2], a[i], sol[k-1])==orar)
                sol[k-1]=a[i], k--;
            k++;
        }
        else
            sol[k]=a[i], k++;
    }
    for(int i=n-2; i>=0; i--)
    {
        if(calcOrientare(sol[k-2], a[i], sol[k-1])==orar)
        {

            while(calcOrientare(sol[k-2], a[i], sol[k-1])==orar)
                sol[k-1]=a[i], k--;
            k++;
        }
        else
            sol[k]=a[i], k++;
    }
    fout<<k-1<<'\n';
    for(int i=k-2; i>=0; i--)
        fout<<fixed<<setprecision(6)<<sol[i].x<<" "<<fixed<<setprecision(6)<<sol[i].y<<'\n';
    return 0;
}