#include <bits/stdc++.h>
#define MAX_NR 1000000100
using namespace std;

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

struct punct
{
    double x,y;
}v[120100],s[120100];

int compare(punct A,punct B)
{
    return ( (A.x - v[1].x)*(B.y - v[1].y) > (A.y-v[1].y)*(B.x-v[1].x) );
}

bool viraj_dreapta(punct A,punct B,punct C)
{
    return ( (A.x*B.y + B.x*C.y + A.y*C.x - B.y*C.x - C.y*A.x - B.x*A.y) < 0);
}

int n,i,poz,T;
double minix=MAX_NR,miniy=MAX_NR;
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i].x>>v[i].y;

        if(v[i].x<minix)
        {
            minix=v[i].x;
            miniy=v[i].y;
            poz=i;
        }
        else if(v[i].x==minix)
        {
            if(v[i].y<miniy)
            {
                miniy=v[i].y;
                poz=i;
            }
        }
    }

    swap(v[1],v[poz]);

    sort(v+2,v+n+1,compare);

    T=2;
    s[1]=v[1];
    s[2]=v[2];
    for(i=3;i<=n;i++)
    {
        while(T>2 && viraj_dreapta(s[T-1],s[T],v[i]))T--;
        T++;
        s[T]=v[i];
    }

    g<<T<<'\n';
    for(i=1;i<=T;i++)
        g<<fixed<<setprecision(6)<<s[i].x<<" "<<fixed<<setprecision(6)<<s[i].y<<'\n';
    return 0;
}