#include<iostream>
#include<fstream>
#include<algorithm>
#include<iomanip>
#define x first
#define y second
using namespace std;
typedef pair<double,double> point;
point st[120005],p,v[120005],aux;
double trig(point a,point b,point c)
{

   // return (double)(b.x-a.x)*(b.y-a.y)-(c.x-a.x)*(c.y-a.y);
     return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
bool cmp(point a, point b)
{

    return(trig(v[1],a,b)<0);

}
int vf,i,n,poz,mini;
int main()
{

    ifstream cin("infasuratoare.in");
    ofstream cout("infasuratoare.out");
    cin>>n;
    for(i=1;i<=n;i++)
    {

        cin>>v[i].x>>v[i].y;
        if(i==1)
        {

            poz=1;
            mini=v[i].y;
        }
        else if(v[i].y<mini)
            mini=v[i].y;

    }
    aux=v[poz];
    v[poz]=v[1];
    v[1]=aux;
    sort(v+2,v+1+n,cmp);
    st[1]=v[1];
    vf=1;
    for(i=2;i<=n;i++)
    {
        while(vf>1&&trig(st[vf-1],st[vf],v[i])>0)
            vf--;
        vf++;
        st[vf]=v[i];
    }
    cout<<vf<<"\n" ;
    for(i=vf;i>=1;i--)
    {

        cout<<fixed<<setprecision(6)<<st[i].x<<" "<<st[i].y<<"\n";
    }
    return 0;
}