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

using namespace std;

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

int n;

struct punct{double x; double y;};

punct p[120003],s[120003];

double det(punct p1, punct p2, punct p3)
{
    return(p1.x*p2.y+p2.x*p3.y+p1.y*p3.x-p2.y*p3.x-p3.y*p1.x-p1.y*p2.x);
}

bool cond(punct p1, punct p2)
{
    double D;
    D=det(p[1],p1,p2);
    return (D>0);
}

int main()
{
    int i,k;
    int j=1;
    f>>n;
    for(i=1;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[j],p[1]);
    sort(p+2,p+n+1,cond);
    s[1]=p[1]; s[2]=p[2];
    k=2;
    for(i=3;i<=n;i++)
    {
        while(det(s[k-1],s[k],p[i])<0) 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';
    return 0;
}