# include <fstream>
# include <algorithm>
# include <iomanip>
# define nmax 120001
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,poz,size;
struct pct
{
    double x,y;
}a[nmax];
int st[nmax];
double det(pct A, pct B, pct C)
{
    return A.x*B.y+B.x*C.y+C.x*A.y-C.x*B.y-A.x*C.y-B.x*A.y;
}
bool cmp(pct A, pct B)
{
    double dx1,dx2,dy1,dy2;
    dy1=A.y-a[1].y;
    dy2=B.y-a[1].y;
    dx1=A.x-a[1].x;
    dx2=B.x-a[1].x;
    if (dy1*dx2 >= dx1*dy2) return 0;
    else return 1;
}
void infasuratoare()
{
    int i;
    st[1]=1; st[2]=2; size=2;
    for(i=3; i<=n; ++i)
    {
        while(size>=2 && det(a[st[size-1]], a[st[size]], a[i])<0)
            size--;
        st[++size]=i;
    }
    g<<size<<"\n";
    for(i=1; i<=size; ++i)
        g<<fixed<<setprecision(6)<<a[st[i]].x<<" "<<a[st[i]].y<<"\n";
}
int main()
{
    int i;
    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();

    return 0;
}