#include<fstream>
#include<algorithm>
#include<iomanip>
#include<cmath>
#define eps 0.000001
using namespace std;
int s[120001],i,n;
bool viz[120001];
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
 
struct punct
{
    double x,y;
}v[120001];
 
 
 
double determinant(punct A,punct B,punct C)
{
    return (B.x-A.x)*(C.y-A.y)-(C.x-A.x)*(B.y-A.y);
}
 
bool cmp(punct a,punct b)
{
     
    return determinant(v[1],a,b)<0;
}
 
 
int main()
{
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    int mini=1;
    for (i=2; i<=n; ++i)
    {
        if (fabs(v[i].x - v[mini].x) > eps) {if (v[i].x < v[mini].x) mini=i;}
        else if (v[i].y < v[mini].y) mini=i;
    }
  
    punct temp = v[1];
    v[1]=v[mini];
    v[mini]=temp;
  
    sort (v+2,v+n+1,cmp);
    /*for(i=2;i<=n;i++)
        if(v[i-1].x==v[i].x&&v[i-1].y==v[i].y)
        {
            for(int j=i;j<=n;j++)
                v[j-1]=v[j];
            i--;
            n--;
        }
    */
    s[1]=1;s[2]=2;viz[2]=1;
    int k=2;
    for(i=3;i<=n;i++)
    {
        while(determinant(v[s[k-1]],v[s[k]],v[i])<=0  && k>1)
        {
            viz[s[k]]=0;s[k]=0;k--;
        }
         
        s[++k]=i;
        viz[i]=1;
    }
    for(i=n-1;i>=1;i--)
    {
        if(!viz[i])
       { while(determinant(v[s[k-1]],v[s[k]],v[i])<=0&&k>1)
        {
            viz[s[k]]=0;s[k]=0;k--;
        }
        s[++k]=i;
        viz[i]=1;}
    }
    g<<k-1<<"\n";
    //for(i=k;i>1;i--)
    for(i=1;i<k;i++)
        g<<fixed<<setprecision(6)<<v[s[i]].x<<" "<<v[s[i]].y<<"\n";
    return 0;
}