# include <fstream>
# include <algorithm>
# include <iomanip>
# define NR 125000
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct elem {
    double x, y;
}a[NR];
bool cmp (elem x, elem y) {
    double dx1, dx2, dy1, dy2;
    dx1=x.x - a[1].x;
    dy1=x.y - a[1].y;

    dx2=y.x - a[1].x;
    dy2=y.y - a[1].y;

    return (dy1*dx2 < dy2*dx1);
}

int i,j,n,m,x,y,VV,poz;
int st[NR];

double det (elem a, elem b, elem c) {
    return a.x*b.y + b.x*c.y + c.x*a.y - a.x*c.y - c.x*b.y - b.x*a.y;
}
void infasuratoare () {
    int i,j;
    st[1]=1; st[2]=2; VV=2;
    for (i=3; i<=n; ++i) {
        while (VV>=2 && det(a[i], a[st[VV-1]], a[st[VV]])<0)
            --VV;
        st[++VV]=i;
    }
}
int main ()
{
    f>>n; poz=1;
    for (i=1; i<=n; ++i) {
        f>>a[i].x>>a[i].y;
        if (a[i].x < a[poz].x) poz=i;
        else if (a[i].x==a[poz].x && a[i].y < a[poz].y) poz=i;
    }
    swap(a[1], a[poz]);
    sort (a+2, a+n+1, cmp);

    infasuratoare ();
     g<<VV<<"\n";
    for (i=1; i<=VV; ++i)
        g<<fixed<<setprecision(6)<<a[st[i]].x<<" "<<a[st[i]].y<<"\n";

    return 0;
}