#include<iostream>
#include<fstream>
#include<algorithm>
#include<iomanip>
using namespace std;

#define NMAX 120001

struct punct {
    double x,y;
};

punct v[NMAX],s[NMAX];

inline double cross_product(punct a, punct b, punct c)
{
    return (double)a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y);
}

inline bool cmp(const punct &a, const punct &b)
{
    return cross_product(v[1],a,b)>0;
}

int graham(int n)
{
    int i,p;
    for(i=2;i<=n;i++)
        if(v[1].x>v[i].x || (v[i].x==v[1].x && v[i].y<v[1].y))
            swap(v[1],v[i]);
    sort(v+2,v+n+1,cmp);
    s[1]=v[1];
    s[2]=v[2];
    p=2;
    for(i=3;i<=n;i++) {
        while(p>=2 && cross_product(s[p-1],s[p],v[i])<0)
            p--;
        s[++p]=v[i];
    }
    return p;
}

int main ()
{
    int n,i,p;
    ifstream f("infasuratoare.in");
    ofstream g("infasuratoare.out");
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    f.close();
    p=graham(n);
    g<<p<<'\n';
    g<<fixed;
    for(i=1;i<=p;i++)
        g<<setprecision(6)<<s[i].x<<" "<<s[i].y<<'\n';
    g.close();
    return 0;
}