#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");
const double eps=1e-14;
const int NMAX=120000;
struct point
{
    double x,y;
}p[NMAX+5],LL;
int h[NMAX+5];
double cp(point p1,point p2,point p3)
{
    return (p2.x-p1.x)*(p3.y-p2.y)-(p2.y-p1.y)*(p3.x-p2.x);
}
int ccw(point p1,point p2,point p3)
{
    double product=cp(p1,p2,p3);
    if(fabs(product)<eps) return 0;
    if(product>=eps) return 1;
    return -1;
}
bool cmp(point a,point b)
{
    if(ccw(LL,a,b)==-1) return 0;
    else return 1;
}
int main()
{
        int n,i;
        cin>>n;
        cin>>p[1].x>>p[1].y;
        for(i=2;i<=n;i++)
        {
            cin>>p[i].x>>p[i].y;
            if(fabs(p[i].y-p[1].y)<eps&&
               p[i].x-p[1].x<=-eps)
                swap(p[1],p[i]);
            else if(p[i].y-p[1].y<=eps) swap(p[1],p[i]);
        } sort(p+2,p+n+1,cmp);
        LL=p[1]; p[n+1]=LL;
       // for(i=1;i<=n+1;i++)
         //   cout<<p[i].x<<" "<<p[i].y<<'\n';
         int top;
         i=3; h[1]=1; h[2]=2; top=2;
         while(i<=n+1)
         {
             if(ccw(p[h[top-1]],p[h[top]],p[i])==-1) top--;
             else {
                h[++top]=i; i++;
             }
         } cout<<top-1<<'\n';
         for(i=1;i<=top-1;i++)
         {
             cout<<fixed<<setprecision(6)<<p[h[i]].x<<" ";
             cout<<fixed<<setprecision(6)<<p[h[i]].y<<'\n';
         }
        cin.close();
        cout.close();
       return 0;
}