#include <algorithm>
#include <iomanip>
#include <fstream>
#define x first
#define y second
using namespace std;
ifstream f("infasuratoare.in"); ofstream g("infasuratoare.out");
typedef pair <double, double> Point;
const int Nmax=120005;
const double EPS=1e-12;
int n,vf,st[Nmax];
Point v[Nmax];
bool vis[Nmax];
void read()
{   f>>n;
    for(int i=1;i<=n;++i) f>>v[i].x>>v[i].y;
}
double Det(Point O, Point A, Point B)
{   return (A.x-O.x)*(B.y-O.y)-(B.x-O.x)*(A.y-O.y);}
void HullAndrew()
{   sort(v+1,v+n+1);
    st[1]=1; st[2]=2; vf=2;
    vis[2]=true;
    for(int i=1,p=1;i; i+=(p=(i==n?-p:p)))
    {   if(vis[i]) continue;
        while(vf>1 && Det(v[st[vf-1]],v[st[vf]],v[i])<EPS) vis[st[vf--]]=false;
        st[++vf]=i;
        vis[i]=true;
    }
    g<<vf-1<<"\n"<< setprecision(6)<<fixed;
    for(int i=1; i<vf; ++i)
        g<<v[st[i]].x <<" "<<v[st[i]].y<<"\n";
}
int main()
{   read(); HullAndrew();}