#include <fstream>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;
ifstream in("infasuratoare.in");
ofstream out("infasuratoare.out");
const int nmax=12e4+10;
const double eps=1.0e-14;
struct point
{
  double x,y;
}p[nmax],ll;
int h[nmax];
double cp(const point &p1,const point &p2,const point &p3)
{
    return(p2.x-p1.x)*(p3.y-p2.y)-(p2.y-p1.y)*(p3.x-p2.x);
}
int ccw(const point &p1,const point &p2,const point &p3)
{
    double crossp=cp(p1,p2,p3);
    if(fabs(crossp)<eps)
        return 0;
    if(crossp>=eps)
        return 1;
    return -1;
}
bool cmp(point &p1,point &p2)
{
    return ccw(ll,p1,p2)>0;
}
double arie_poligon(int n)
{
    double aria=0;
    int i;
    p[n]=p[0];
    for(i=0;i<n;i++)
        aria+=p[i].x*p[i+1].y-p[i+1].x*p[i].y;
    aria=fabs(aria)*0.5;
    return aria;
}
int main()
{
    int n,i,top,j;
    double a,b;
    in>>n>>a>>b;
    p[0].x=a;
    p[0].y=b;
    for(i=1;i<n;i++)
    {
        in>>p[i].x>>p[i].y;
        if(p[i].y-p[0].y<=-eps  ||  (fabs(p[i].y-p[0].y)<eps  &&  p[i].x-p[0].x<=-eps))
            swap(p[0],p[i]);
    }
    ll=p[0];
    sort(p+1,p+n,cmp);
    p[n]=p[0];
    h[0]=0;
    h[1]=1;
    top=1;
    i=2;
    while(i<=n)
    {
        if(ccw(p[h[top-1]],p[h[top]],p[i])>0)
            h[++top]=i++;
        else
            top--;
    }
    out<<top<<"\n";
    for(i=0;i<top;i++)
        out<<fixed<<setprecision(6)<<p[h[i]].x<<" "<<p[h[i]].y<<"\n";
    return 0;
}