#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;

}