#include <fstream>
#include <algorithm>
#include <iomanip>
#include <cmath>
using namespace std;
ifstream fin ("data.in");
ofstream fout ("data.out");
struct POINT{
    double x,y;
};
const int NMAX=120000;
const double eps=1.0e-14;
POINT P[NMAX+5],LL;
int h[NMAX+5];
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);
}
double ccw(const POINT& P1, const POINT& P2, const POINT& P3)
{
    double crossprod=cp(P1,P2,P3);
    if(fabs(crossprod)<eps)
        return 0;
    if(crossprod>=eps)
        return 1;
    return -1;
}
bool cmp(POINT & P1, POINT & P2){
    return ccw(LL,P1,P2)>0;
}

double arie_poligon(int n){
    double aria; int i;
    P[n]=P[0];
    aria=0;
    for(i=0;i<n;i++)
        aria=P[i].x*P[i+1].y-P[i+1].x*P[i].y;
    aria=0.5*fabs(aria);
    return aria;
}
int main()
{
    int n,i,top;
    double a,b;
    fin>>n>>a>>b;
    P[0].x=a; P[0].y=b;
    for(i=1;i<=n;i++)
    {
        fin>>a>>b;
        P[i].x=a;
        P[i].y=b;
        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[i], P[0]);
    }
    LL=P[0];
    P[n]=P[0];
    h[0]=0;
    h[1]=1;
    sort(P+1, P+n, cmp);
    top=1; i=2;
    while(i<=n)
    {
        if(ccw(P[h[top-1]], P[h[top]], P[i])>0)
        {
            h[++top]=i;
            ++i;
        }
        else
        {
            --top;
        }
    }
        fout<<top<<'\n';
        for(i=0;i<top;++i)
            fout<<fixed<<setprecision(6)<<P[h[i]].x<<" "<<setprecision(6)<<P[h[i]].y<<'\n';

    return 0;
}