#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

struct ura
{
    double x,y;
    short arie=0;
} v[120002],s[120002];

int cearie(double xa, double ya, double xb, double yb, double xc, double yc)
{
    double ari;
    ari=xa*yb+xb*yc+xc*ya-ya*xb-yb*xc-yc*xa;
    if(ari<0)
        return -1;
    if(ari>0)
        return 1;
    return 0;

}

bool sortare(ura a, ura b)
{
    if(a.x<b.x)
    {
        return true;
    }
    else if(a.x==b.x && a.y<b.y)
    {
        return true;
    }
    return false;
}

int main()
{
    int n,vf=0;
    cin>>n;
    for(int i=1; i<=n; i++)
    {
        cin>>v[i].x>>v[i].y;
    }
    sort(v+1,v+n+1,sortare);
    v[1].arie=0;
    v[n].arie=0;
    for(int i=2; i<n; i++)
    {
        v[i].arie=cearie(v[1].x,v[1].y,v[n].x,v[n].y,v[i].x,v[i].y);
    }
    s[++vf]=v[1];
    for(int i=2; i<=n; i++)
    {
        if(v[i].arie<=0)
        {
            if(vf<2)
            {
                s[++vf]=v[i];
            }
            else
            {
                while(vf>=2 && cearie(s[vf-1].x,s[vf-1].y,s[vf].x,s[vf].y,v[i].x,v[i].y)==-1)
                {
                    vf--;
                }
                vf++;
                s[vf]=v[i];
            }
        }
    }
    int x=vf;
    for(int i=n-1; i>0; i--)
    {
        if(v[i].arie>=0)
        {
            if(vf<=x+1)
            {
                s[++vf]=v[i];
            }
            else
            {
                while(vf>=x+1 && cearie(s[vf-1].x,s[vf-1].y,s[vf].x,s[vf].y,v[i].x,v[i].y)==-1)
                {
                    vf--;
                }
                vf++;
                s[vf]=v[i];
            }
        }
    }

    cout<<vf-1<<"\n";
    for(int i=2; i<=vf; i++)
    {
        cout<<fixed<<setprecision(12)<<s[i].x<<" "<<s[i].y<<'\n';
    }
    return 0;
}