#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)
{
    return ((a.x*b.y)+(b.x*c.y)+(a.y*c.x)-(b.y*c.x)-(a.x*c.y)-(b.x*a.y));
}

bool comp(punct i, punct j)
{
    double D;
    D=determinant(p[1],i,j);
    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);
    S[1]=p[1]; S[2]=p[2]; K=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';
    f.close();
    g.close();
    return 0;
}