#include <fstream>
#include <algorithm>
#include <iomanip>
#define nmax 120010

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct punct{
double x,y;
} a[nmax],stk[nmax],minim;
int n,i,poz,vf;

double delta(punct A, punct B, punct C)
{
    return (B.x-A.x)*(C.y-A.y)-(B.y-A.y)*(C.x-A.x);
}

class cmp
{
public:
    bool operator()(punct A, punct B)
    {
        return delta(a[1],A,B)<0;
    }
};

int main()
{
    fin >> n;
    minim.x=minim.y=1000000010;
    for (i=1; i<=n; i++)
    {
        fin >> a[i].x >> a[i].y;
        if (a[i].x<minim.x||(a[i].x==minim.x&&a[i].y<minim.y))
            minim=a[i],poz=i;;
    }
    swap(a[1],a[poz]);
    sort(a+2,a+n+1,cmp());
    stk[vf]=a[1];
    stk[++vf]=a[2];
    for (i=3; i<=n; i++)
    {
        while (vf>0&&delta(stk[vf-1],stk[vf],a[i])>0)
            vf--;
        stk[++vf]=a[i];
    }
    fout << vf+1 << '\n';
    for (i=vf; i>=0; i--)
        fout << fixed << setprecision(12) << stk[i].x << ' ' << stk[i].y << '\n';
}