#include <fstream>
#include<algorithm>
#include<iomanip>
using namespace std;
ifstream cin ("infasuratoare.in");
ofstream cout ("infasuratoare.out");
int n;
struct bla
{
    double x,y;
} date[150100];
int used[150100];
int st[150100];
int vf;
bool sortare (bla q,bla w)
{
    if(q.x==w.x) return q.y<w.y;
    return q.x<w.x;
}
void read ()
{
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>date[i].x>>date[i].y;
        sort(date+1,date+n+1,sortare);
}
int ec_dreptei (bla a,bla b,bla c)
{
    return (c.x-a.x)*(a.y-b.y)-(a.x-b.x)*(c.y-a.y);
}
void convex ()
{
    vf=2;
    st[1]=1;
    st[2]=2;
    used[2]=1;
    int urm=3,sens=1;
    while(used[1]==0)
    {
        while(used[urm]!=0)
        {
            if(urm==n) sens=-1;
            urm+=sens;
        }
        while(vf>1 && ec_dreptei(date[st[vf-1]],date[st[vf]],date[urm])<0) used[st[vf--]]=0;
        st[++vf]=urm;
        used[urm]=1;
    }
}
void write ()
{
    cout<<vf-1<<"\n";
    for(int i=1;i<vf;i++)
    {
        cout<<fixed<<setprecision(12)<<date[st[i]].x<<" "<<date[st[i]].y<<"\n";
    }
}
int main()
{
    read();
    convex();
    write();
    cin.close();
    cout.close();
    return 0;
}