#include <algorithm>
#include <fstream>
#include <iomanip>
#define x first
#define y second
using namespace std;
typedef pair<double, double> Point;
ifstream f("infasuratoare.in"); ofstream g("infasuratoare.out");
const int Nmax=120005;
Point v[Nmax],St[Nmax];
int n,Vf;
void read()
 {  f>>n;
    for(int i=1;i<=n;++i) f>>v[i].x >>v[i].y;
}
inline double det(const Point& A, const Point& B, const Point& C)
{   return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);}
inline int cmp(const Point& p1, const Point& p2)
{   return det(v[1], p1, p2)<0;}
void SortPct()
{   int i,pos = 1;
    for(i=2;i<=n;++i)
        if(v[i]<v[pos]) pos=i;
    swap(v[1],v[pos]);
    sort(v+2,v+n+1,cmp);
}
void Hull()
{   SortPct();
    St[1]=v[1]; St[2]=v[2]; Vf=2;
    for(int i=3;i<=n;++i)
    {   while(Vf>=2 && det(St[Vf-1],St[Vf],v[i])>0) --Vf;
        St[++Vf]=v[i];
    }
}
void write()
{   g<<fixed<<Vf<<"\n";
    for(int i=Vf;i;--i) g<<setprecision(9)<<St[i].x<<" "<<St[i].y<<"\n";
}
int main()
{   read(); Hull(); write();}