#include <fstream>
#include <algorithm>
#include <iomanip>

using namespace std;

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

int n,poz,vf,stiva[120500];

struct punct{
  double x,y;
}v[120500],p;

int position(punct p1, punct p2)
{
    int val = (p2.x - p.x) * (p1.y - p.y) - (p2.y - p.y) * (p1.x - p.x);
    if(val <=0) return 1;
    return 0;
}
int main()
{
    f>>n;
    p.x = p.y = 1000000003;
    for(int i = 1; i<=n ; i++) { f>>v[i].x>>v[i].y;
                                 if(v[i].x < p.x || (v[i].x == p.x && v[i].y < p.y)) {
                                    p.x = v[i].x;
                                    p.y = v[i].y;
                                    poz = i;
                                 }
                               }
    swap(v[1],v[poz]);

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

    //pana aici e bine


    stiva[++vf] = 1;
    stiva[++vf] = 2;
    v[n+1] = v[1];
    for(int i = 3; i<=n+1; i++)
    {
        p = v[stiva[vf-1]];
        while(!position(v[stiva[vf]],v[i]) && vf>1) {
            vf--;
            p = v[stiva[vf-1]];
        }
        stiva[++vf] = i;
    }
    g<<vf-1<<setprecision(6)<<fixed<<'\n';
    for(int i = 2; i<=vf-1 ; i++) g<<v[stiva[i]].x<<' '<<v[stiva[i]].y<<'\n';
    g<<v[stiva[1]].x<<' '<<v[stiva[1]].y<<'\n';
    return 0;
}