#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct pct
{
    double x,y;
}a[120005],Min;

int n,q[120005],poz;

bool cmp(pct b,pct c)
{
    return 1ll*(a[0].y-b.y)*(a[0].x-c.x)<1ll*(a[0].y-c.y)*(a[0].x-b.x);
}





int main()
{
    fin>>n;
    Min.y=Min.x=1000000000;
    for(int i=0;i<n;i++)
    {
        fin>>a[i].x>>a[i].y;
        if(a[i].x<Min.x)
        {
            Min=a[i];
            poz=i;
        }
        else
        if(a[i].x==Min.x&&a[i].y<Min.y)
        {
            Min=a[i];
            poz=i;
        }
    }
    swap(a[poz],a[0]);
    sort(a+1,a+n,cmp);
    q[1]=0;
    q[2]=1;
    int k=2;
    for(int i=2;i<n;i++)
    {
        while(k>=2&&1ll*(a[i].y-a[q[k]].y)*(a[i].x-a[q[k-1]].x)<1ll*(a[i].y-a[q[k-1]].y)*(a[i].x-a[q[k]].x))
            k--;
        q[++k]=i;
    }
    fout<<k;
    for(int i=1;i<=k;i++)
        fout<<"\n"<<fixed<<setprecision(6)<<a[q[i]].x<<" "<<a[q[i]].y;
    return 0;
}