#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f ("infasuratoare.in");
ofstream g ("infasuratoare.out");
const int nmax=12e4+3;
struct usu
{
    long double x,y;
}v[nmax];
int n,sol[nmax],k;
inline long double det(const usu &t1,const usu &t2,const usu &t3)
{
    return t1.x*t2.y+t2.x*t3.y+t3.x*t1.y-t3.x*t2.y-t1.x*t3.y-t2.x*t1.y;
}
inline bool cmp(const usu &t1,const usu &t2)
{
    return det(v[1],t1,t2)<0;
}
int main()
{
    f>>n;
    f>>v[1].x>>v[1].y;
    for(int i=2;i<=n;++i)
    {
        f>>v[i].x>>v[i].y;
        if(v[i].x<v[1].x)
        {
            swap(v[1],v[i]);
            continue;
        }
        else if(v[i].x==v[1].x&&v[i].y<v[1].y) swap(v[1],v[i]);
    }
    sort(v+2,v+n+1,cmp);
    sol[++k]=1;
    sol[++k]=2;
    for(int i=3;i<=n;++i)
    {
        while(k>2&&det(v[sol[k-1]],v[sol[k]],v[i])>0) --k;
        sol[++k]=i;
    }
    g<<k<<'\n';
    for(int i=k;i>=1;--i) g<<fixed<<setprecision(6)<<v[sol[i]].x<<' '<<v[sol[i]].y<<'\n';
    return 0;
}