#include <iostream>
#include <fstream>
#include <algorithm>

#define oo 0x3f3f3f
#define Lg 120010

using namespace std;

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

long n,start,la,lst = 1;
double x[Lg], y[Lg];
int st[Lg], a[Lg];

bool comp(int i,int j)
{
    long double A = (x[i]-x[start])*(y[j]-y[start]);
    long double B = (x[j]-x[start])*(y[i]-y[start]);
    return (A<B);
}

long double fd(int i1, int i2, int i3)
{
    return (long double)(x[i1]*y[i2] + x[i2]*y[i3] + x[i3]*y[i1] - y[i1]*x[i2] - y[i2]*x[i3] - y[i3]*x[i1]);
}

void citire()
{
    f>>n;
    x[0]=y[0]=oo;
    for(int i=1;i<=n;i++)
    {
        f>> x[i] >> y[i];

        if(x[i] < x[start])
            start=i;
        else
            if(x[i] == x[start])
                if(y[i] < y[start])
                    start=i;
    }
}

void ordoneaza()
{
    la=0;
    for(int i=1;i<=n;i++)
    {
      if (i != start)
            a[++la] = i;
    }
    sort(a+1,a+la+1,comp);
}


void solve()
{
    st[lst]=start;
    for(int i=1;i<=la;i++)
    {
        if(a[i]!=start)
        {
            while(lst>1 && fd(st[lst-1],st[lst],a[i]) > 0)
                --lst;
            st[++lst] = a[i];
        }
    }
    st[++lst]=start;

    reverse(st+1,st+lst+1);

    g << lst-1 << "\n";

    for(int i=1;i<lst;i++)
        g << x[st[i]] << " " << y[st[i]] << "\n";

}

int main()
{
    citire();
    ordoneaza();
    solve();

    return 0;
}