#include <fstream>
#include <algorithm>
#include<iomanip>

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

int n,k;

struct punct{double x; double y;}p[120003];

punct s[120003];

double determinant(punct a, punct b, punct c)
{
    double D;
    D=(a.x*b.y)+(b.x*c.y)+(c.x*a.y)-(c.x*b.y)-(a.x*c.y)-(a.y*b.x);
    return D;
}


bool comp(punct p1, punct p2)
{
    double D;
    D=determinant(p[1],p1,p2);
    if(D>0) return true;
    return false;
}

int main()
{
    int i,j;
    f>>n;
    f>>p[1].x>>p[1].y;
    j=1;
    for(i=2;i<=n;i++)
    {
        f>>p[i].x>>p[i].y;
        if(p[i].x<p[j].x || (p[i].x==p[j].x && p[i].y<p[j].y)) j=i;
    }
    swap(p[1],p[j]);
    sort(p+2,p+n+1,comp);
    k=2;
    s[1]=p[1]; s[2]=p[2];
    for(i=3;i<=n;i++)
    {
        while(k>1 && determinant(s[k-1],s[k],p[i])<0) k--;
        k++; s[k]=p[i];
    }
    g<<k<<'\n';
    g<<fixed;
    for(i=1;i<=k;i++) g<<setprecision(6)<<s[i].x<<' '<<setprecision(6)<<s[i].y<<'\n';
    g<<'\n';
    f.close();
    g.close();
    return 0;
}