#include <bits/stdc++.h>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
const int NMAX=120005;
int n,head;
struct Point
{
    double x,y;
    friend bool operator<(Point A,Point B)
    {
        if(A.x<B.x)
            return 1;
        if(A.x==B.x && A.y<B.y)
            return 1;
        return 0;
    }
}points[NMAX],st[NMAX];
double cross_product(Point O,Point A,Point B)
{
    return (A.x-O.x)*(B.y-O.y)-(B.x-O.x)*(A.y-O.y);
}
bool cmp(Point A,Point B)
{
    return cross_product(points[1],A,B)<0;
}
void sort_points()
{
    int pos=1;
    for(int i=2; i<=n; i++)
        if(points[i]<points[pos])
            pos=i;
    swap(points[1],points[pos]);
    sort(points+2,points+n+1,cmp);
}
void convex_hull()
{
    sort_points();
    st[1]=points[1];
    st[2]=points[2];
    head=2;
    for(int i=3;i<=n;i++)
    {
        while(head>=2 && cross_product(st[head-1],st[head],points[i])>0)
            head--;
        st[++head]=points[i];
    }
}
int main()
{
    f>>n;
    for(int i=1; i<=n; i++)
        f>>points[i].x>>points[i].y;
    convex_hull();
    g<<head<<'\n';
    for(int i=head; i>=1; i--)
        g<<setprecision(6)<<fixed<<st[i].x<<' '<<st[i].y<<'\n';
    return 0;
}