#include <bits/stdc++.h>
#define MAX 120120
#define INF 999999999.0
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct poz
{
    double x,y;
};
poz v[MAX];
poz st[MAX];
double xmin=INF,ymin=INF;
int n,start,vf;
double determ(poz a,poz b,poz c)
{
    return (b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y);
}
bool compar(poz a,poz b)
{
    return determ(v[1],a,b)<0;
}
void rd();
void hall();
void wr();
int main()
{
    rd();
    hall();
    wr();
    return 0;
}
void rd()
{
    int i;
    fin>>n;
    for(i=1; i<=n; i++)
    {
        fin>>v[i].x>>v[i].y;
        if(v[i].x<xmin)
        {
            start=i;
            xmin=v[i].x;
            ymin=v[i].y;
        }
        else if(v[i].x==xmin&&v[i].y<ymin)
        {
            start=i;
            ymin=v[i].y;
        }
    }
    swap(v[1],v[start]);
    sort(v+2,v+n+1,compar);
}
void hall()
{
    int i;
    st[1]=v[1];
    st[2]=v[2];
    vf=2;
    for(i=3; i<=n; i++)
    {
        while(vf>=2&&determ(st[vf-1],st[vf],v[i])>0)
            vf--;
        st[++vf]=v[i];
    }
}
void wr()
{
    int i;
    fout<<vf<<'\n';
    fout<<setprecision(6)<<fixed;
    for(i=vf;i>=1;i--)
        fout<<st[i].x<<' '<<st[i].y<<'\n';
}