#include <bits/stdc++.h>
#define inf 1000000001
using namespace std;

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

struct infasuratoare
{
    double x,y;
}v[120100],sol[120100];

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

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

int n,i,punct,t;
double minix=inf,miniy=inf;
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;
            punct=i;
        }
        else if(v[i].x==minix)
        {
            if(v[i].y<miniy)
            {
                miniy=v[i].y;
                punct=i;
            }
        }
    }
    swap(v[punct],v[1]);
    sort(v+2,v+n+1,compare);

    t=2;
    sol[1]=v[1];
    sol[2]=v[2];
    for(i=3;i<=n;i++)
    {
        while(t>2 && viraj_dreapta(sol[t-1],sol[t],v[i]))t--;
        t++;sol[t]=v[i];
    }
    g<<t<<'\n';
    for(i=1;i<=t;i++)
        g<<fixed<<setprecision(12)<<sol[i].x<<" "<<fixed<<setprecision(12)<<sol[i].y<<'\n';
    return 0;
}