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

struct punct{
       double x;
       double y;
};

const int MAX_N = 120005;

int st[MAX_N],k;
bool viz[MAX_N];
punct a[MAX_N];
int i,n,p;

short int semn(const punct &A, const punct &B, const punct &P){
      double x = (B.x*P.y + A.x*B.y + A.y*P.x - B.x*A.y - P.x*B.y - P.y*A.x);
      if(x>0) return 1;
      if(x<0) return (-1);
      return 0;
}

bool comp(const punct &a, const punct &b){
     if(a.x==b.x) return (a.y<b.y);
     else return (a.x<b.x);
}

int main(){
    fi>>n;
    for(i=1;i<=n;i++) fi>>a[i].x>>a[i].y;
    
    sort(a+1,a+n+1,comp);
    
    st[1]=1; st[2]=2; k=2; 
    viz[1]=0; viz[2]=1;
    for(i=3,p=1; i>0; i+=(p=(i==n)?(-p):(p)))
     if(!viz[i]){
                 while(k>=2 && semn(a[st[k-1]],a[st[k]],a[i])<=0) viz[st[k--]]=0; 
                 st[++k]=i; 
                 viz[i]=1;
                }
    
    k--;
    fo<<k<<'\n';
    for(i=1;i<=k;i++)
      fo<<fixed<<setprecision(8)<<a[st[i]].x<<' '<<a[st[i]].y<<'\n';
    
    fi.close();
    fo.close();
    return 0;
}