#include<fstream>
#include<algorithm>
#include<iomanip>
#define NMax 120005
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct Point
{
    double x,y;
};

int N,Top;
Point V[NMax],S[NMax];

void Read()
{
    fin>>N;

    for(int i = 1 ; i <= N ; ++i)
        fin>>V[i].x>>V[i].y;
}

double Area(Point A,Point B,Point C)
{
    return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

bool Comp(Point A,Point B)
{
    return (Area(V[1],A,B) < 0);
}

void Solve()
{
    int pos = 1;

    for(int i = 2 ; i <= N ; ++i)
        if(V[i].y < V[pos].y || (V[i].y == V[pos].y && V[i].x < V[pos].x))
            pos = i;

    swap(V[1],V[pos]);

    sort(V+2,V+N+1,Comp);

    S[1] = V[1];
    S[2] = V[2];
    Top = 2;

    for(int i = 3 ; i <= N ; ++i)
    {
        while(Top >= 2 && Area(S[Top - 1],S[Top],V[i]) > 0)
            Top--;
        S[++Top] = V[i];
    }
}

void Print()
{
    fout<<Top<<"\n";

    fout<<fixed<<setprecision(6)<<S[1].x<<" "<<S[1].y<<"\n";

    for(int i = Top ; i >= 2 ; --i)
        fout<<fixed<<setprecision(6)<<S[i].x<<" "<<S[i].y<<"\n";
}

int main()
{
    Read();
    Solve();
    Print();

    fin.close();
    fout.close();
    return 0;
}