//Convex Hull - O(NlogN) - with CrossProduct
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdio>
#include <algorithm>
#define Precizie 1000000000000LL
#define eps 0.0000000000001
#define Nmax 120099
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int N,k;
struct point {double x,y;}P[Nmax],st[Nmax];

inline void ReadInput(),PrintOutPut();
inline bool Equal(double x,double y),LessThan(double x,double y);

inline double CrossProduct(point A,point B,point C)
{
    return (B.x-A.x)*(C.y-A.y)-(B.y-A.y)*(C.x-A.x);
};

struct cmp
{
    bool operator()(const point &A,const point &B)const
    {
        return LessThan(0,CrossProduct(P[1],A,B));
    };
};

inline void ConvexHull()
{
    sort( P+2, P+1+N , cmp() ); // sortez in raport cu primul punct
    k=2 , st[1]=P[1] , st[2]=P[2];
    for(int i=3;i<=N;++i)
    {
        while(k>=2 && LessThan(CrossProduct(st[k-1],st[k],P[i]),0))--k;
        st[++k]=P[i];
    }
}



int main()
{
    ReadInput();
    ConvexHull();
    PrintOutPut();
    return 0;
}

inline bool Equal(double x,double y)
{
    if(fabs(x-y)<eps)return 1;
    else return 0;
}

inline bool LessThan(double x,double y)
{
    if(1LL*Precizie*x<1LL*Precizie*y)return 1;
    else return 0;
}

void ReadInput()
{
    int j=1; // j va fi unde gasesc punctul cu ymin (xmin)
    f>>N;
    f>>P[1].x>>P[1].y;
    for(int i=2;i<=N;++i)
    {
        f>>P[i].x>>P[i].y;
        if(LessThan(P[i].y,P[j].y))j=i;
            else if(Equal(P[i].y,P[j].y) && LessThan(P[i].x,P[j].x))j=i;
    }
    swap(P[1],P[j]);
}

void PrintOutPut()
{
    //solutia a fost generata in ordine trigonometrica
    g<<k<<'\n';
    g.precision(6);
    for(int i=1;i<=k;++i)
        g<<fixed<<st[i].x<<' '<<st[i].y<<'\n';
}