#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct coord
{
    double x,y;
};
coord v[120002];
double m(coord a,coord b,coord c)
{
    return (c.x-a.x)*(b.y-a.y)-(b.x-a.x)*(c.y-a.y);
}
int cmp(coord x,coord y)
{
    if(m(v[1],x,y)>0)
        return 1;
    return 0;
}

int main()
{
    int n,poz=1,st[120002],vf,i;
    fin>>n;
    for (i=1; i<=n; i++)
    {
        fin>>v[i].x>>v[i].y;
        if (v[i].x<v[poz].x || v[i].x==v[poz].x && v[i].y<v[poz].y)
        {
            poz=i;
        }
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    st[1]=1;
    st[2]=2;
    vf=2;
    for (i=3; i<=n; i++)
    {
        while (vf>=2 && m(v[st[vf-1]],v[st[vf]],v[i])<0)
            vf--;
        st[++vf]=i;
    }
    fout<<vf<<'\n';
    for (int i=vf; i>=1; i--)
        fout<<fixed<<setprecision(6)<<v[st[i]].x<<" "<<v[st[i]].y<<"\n";
    return 0;
}