#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct punct
{
    double x,y;
}a[120011];
bool cmp(punct x,punct y)
{
    if(x.x==y.x)
        return x.y<y.y;
    return x.x<y.x;
}
double produs(punct x,punct x1,punct x2)
{
    return (x1.x-x.x)*(x2.y-x.y)-(x2.x-x.x)*(x1.y-x.y);
}
const double EPS=1e-12;
int n,i,q[120011],l,p;
bool v[120011];
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
        f>>a[i].x>>a[i].y;
    sort(a+1,a+n+1,cmp);
    q[1]=1;
    q[2]=2;
    l=2;
    v[2]=1;
    for(i=1,p=1;i>0;i=i+(p=(i==n ? -p:p)))
    {
        if(v[i]==0)
        {
            while(l>=2 && produs(a[q[l-1]],a[q[l]],a[i])<EPS)
            {
                v[q[l]]=0;
                l--;
            }
            l++;
            q[l]=i;
            v[i]=1;
        }
    }
    g<<l-1<<'\n';
    for(i=1;i<l;i++)
        g<<fixed<<setprecision(6)<<a[q[i]].x<<" "<<a[q[i]].y<<'\n';
    return 0;
}