#include <fstream>
#include <algorithm>
#include <iomanip>
#define x first
#define y second
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

typedef pair<double,double>Punct;
Punct p[120001],st[120001];

int n, k;

inline double Rotation(const Punct& P1, const Punct& P2, const Punct& P3)
{
    return (P2.x-P1.x)*(P3.y-P1.y)-(P3.x-P1.x)*(P2.y-P1.y);
}

bool cmp(const Punct& A, const Punct& B)
{
    return Rotation(p[1],A,B)<0;
}

int main()
{
    fin>>n;
    int pos=1;
    for(int i = 1; i<= n; i++ )
    {
        fin>>p[i].x>>p[i].y;
        if(p[i]<p[pos])
            pos=i;
    }
    swap(p[1], p[pos]);
    sort(p+2,p+n+1,cmp);

    st[++k]=p[1];
    st[++k]=p[2];
    for(int i = 3; i<= n; i++ )
    {
        while(k>=2 && Rotation(st[k-1],st[k],p[i])>0)
            k--;
        st[++k]=p[i];
    }
    fout<<k<<'\n';
    for(int i = k; i>0; i-- )
        fout<<setprecision(12)<<fixed<<st[i].x<<  ' ' <<st[i].y<<'\n';
    fin.close();
    fout.close();
    return 0;
}