#include <iostream>
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
using namespace std;
struct punct
{
    double x,y;
};
punct v[120005],stiva[120005];
int n,poz,nr;
double test_orientare(const punct &P0,const punct &P1,const punct &P2)
{
    return (P0.x-P1.x)*(P1.y-P2.y)-(P1.x-P2.x)*(P0.y-P1.y);
}
bool cmp(const punct &P1,const punct &P2)
{
    return test_orientare(v[1],P1,P2)>0;
}
int main()
{
    int i;
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;
 
    }
    poz=1;
    for(i=2;i<=n;i++)
    {
        if(v[i].y<v[poz].y)
        {
            poz=i;
        }
        else
        {
            if(v[i].y==v[poz].y)
            {
                if(v[i].x<v[poz].x)
                {
                    poz=i;
                }
            }
        }
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    stiva[1]=v[1];
    stiva[2]=v[2];
    nr=2;
    for(i=3;i<=n;i++)
    {
        while(nr>=2 && test_orientare(stiva[nr-1],stiva[nr],v[i])<0)
        {
            nr--;
        }
        nr++;
        stiva[nr]=v[i];
    }
    g<<nr<<"\n";
    for(i=2;i<=nr;i++)
    {
        g<<fixed<<setprecision(9)<<stiva[i].x<<" "<<stiva[i].y<<"\n";
    }
    g<<v[1].x<<" "<<v[1].y;
    return 0;
}