#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdio>
#include <algorithm>
#define Precizie 1000000
#define eps 0.0000001
#define Nmax 120099
using namespace std;
ifstream f("infasuratoare.in");

int N,k;

struct point {double x,y;}P[Nmax],st[Nmax],G;

inline void ReadInput(),PrintOutPut();
inline double CrossProduct(const point &A,const point &B,const point &C);
inline bool Equal(const double &x,const double &y),LessThan(const double &x,const double &y);
inline void ConvexHull();

int main()
{
    freopen("infasuratoare.out","w",stdout);
    ReadInput();
    ConvexHull();
    PrintOutPut();
    return 0;
}

struct cmp
{
    bool operator()(const point &A,const point &B)const
    {
        return atan2(A.y-G.y,A.x-G.x)<atan2(B.y-G.y,B.x -G.x);
    };
};

inline void ConvexHull()
{
    sort(P+1,P+1+N,cmp());
    st[1]=P[1],st[2]=P[2];
    k=2;
    for(int i=3;i<=N;++i)
    {
        while(k>=2 && CrossProduct(st[k-1],st[k],P[i])<0)--k;
        st[++k]=P[i];
    }
}
inline double CrossProduct(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 bool Equal(const double &x,const double &y)
{
    if(fabs(x-y)<eps)return 1;
    else return 0;
}

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

void ReadInput()
{
    f>>N;
    f>>P[1].x>>P[1].y;
    G.x+=P[1].x,G.y+=P[1].y;
    for(int i=2;i<=N;++i)
    {
        f>>P[i].x>>P[i].y;
        G.x+=P[i].x,G.y+=P[i].y;
    }
    G.x=1.0*G.x/N,G.y=1.0*G.y/N;

}
void PrintOutPut()
{
    //solutia a fost generata in ordine trigonometrica
    printf("%d\n",k);
    for(int i=1;i<=k;++i)printf("%0.6f %0.6f\n",st[i].x,st[i].y);
}