#include <fstream>
#include <algorithm>
#include <iomanip>
#define x first
#define y second
using namespace std;

typedef pair<double,double>Punct;

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

int n, i, k, poz;
Punct v[120010], st[120010];

double unghipolar (const Punct &A, const Punct &B, const Punct &C)
{
    return (B.x-A.x)*(C.y-A.y)-(B.y-A.y)*(C.x-A.x);
}
bool compar(const Punct &p1, const Punct &p2)
{
    return (unghipolar(v[1],p1,p2)<0);
}

int main()
{
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    poz=1;
    for(i=2;i<=n;i++)
        if(v[i]<v[poz])
            poz=i;
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,compar);
    st[1]=v[1];
    st[2]=v[2];
    k=2;
    for(i=3;i<=n;i++)
        {
            while(k>=2 && unghipolar(st[k-1],st[k],v[i])>0)
                k--;
            st[++k]=v[i];
        }
    g<<fixed;
    g<<k<<'\n';
    for(i=k;i>=1;i--)
        g<<setprecision(9)<<st[i].x<<' '<<st[i].y<<'\n';
    return 0;
}