#include <fstream>
#include <algorithm>
#include <math.h>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.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)///aria paralelogramului
{
    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)///sensul vectorial
{
    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;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);
}
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[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;
    }
    fout<<top<<"\n";
    for(i=0;i<top;i++)
        fout<<fixed<<setprecision(6)<<P[h[i]].x<<" "<<P[h[i]].y<<"\n";
    return 0;
}