#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");
const double eps=1.0e-14;
const double INF=1e9;
const int NMAX=120000;
struct POINT
{
    double x,y;
}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);
}
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;
    P[n]=P[0];
    for(int 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;
    double a,b;
    cin>>n>>a>>b;
    P[0].x=a;
    P[0].y=b;
    for(i=1;i<=n;i++)
    {
        cin>>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[0],P[i]);
    }
    LL=P[0];
    sort(P+1,P+n,cmp);
    P[n]=P[0];
    h[0]=0;
    h[1]=1;
    int 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--;
    }
    cout<<top<<'\n';
    for(int i=0;i<top;i++)
        cout<<fixed<<setprecision(6)<<P[h[i]].x<<" "<<P[h[i]].y<<'\n';
    return 0;
}