#include <fstream>
#include <algorithm>
#include <iomanip>
#include <iostream>

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

typedef double ld;

struct point
{
    ld x;
    ld y;
};
ld trapez(point a,point b)
{
    return (a.y+b.y)*(b.x-a.x);
}
ld arie(point a,point b,point c)
{
    return trapez(a,b)+trapez(b,c)+trapez(c,a);
}
bool cmp(point a,point b)
{
    if(a.x==b.x)
        return a.y<b.y;
    return a.x<b.x;
}
const int N=120000;
int n;
point v[N+5];
point stiva[N+5];
point stiva2[N+5];
int vf=0,nr;

int main()
{
    fin>>n;
    for(int i=1;i<=n;i++)
        fin>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    stiva[++vf]=v[1];
    for(int i=2;i<=n;i++)
    {
        while(vf>1 && arie(stiva[vf-1],stiva[vf],v[i])<0)
            vf--;
        stiva[++vf]=v[i];
    }
    nr=vf;
    vf=0;
    stiva2[++vf]=v[n];
    for(int i=n-1;i>=1;i--)
    {
        while(vf>1 && arie(stiva2[vf-1],stiva2[vf],v[i])<0)
            vf--;
        stiva2[++vf]=v[i];
    }
    fout<<nr+vf-2<<"\n";
    for(int i=1;i<=nr;i++)
        fout<<fixed<<setprecision(6)<<stiva[i].x<<" "<<stiva[i].y<<"\n";
    for(int i=2;i<vf;i++)
        fout<<fixed<<setprecision(6)<<stiva2[i].x<<" "<<stiva2[i].y<<"\n";
    return 0;
}