//HullAndrew
#include<fstream>
#include<iomanip>
#include<algorithm>
#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 A, Point B, Point C)
{
    return (B.x-A.x)*(C.y-A.y)-(B.y-A.y)*(C.x-A.x);
}
void HullAndrew()
{
    sort(v+1,v+n+1);
    st[1]=1;
    st[2]=2;
    vf=2;
    vis[2]=true;
    for(int i=1,p=2;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();
}