#include <bits/stdc++.h>
#define DMAX 120010

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

struct pct
       {
        double x,y;
       }V[DMAX];

vector <pct> S;
int n;

void citire();
void afisare();
double Cross_prod(pct P,pct A,pct B);
void Graham_scam();

bool compar(pct A,pct B)
     {
         return Cross_prod(V[1],A,B)<0;
     }
int main()
{citire();
 Graham_scam();
 afisare();
 return 0;
}
double Cross_prod(pct P,pct A,pct B)
{
 return (A.x-P.x)*(B.y-P.y)-(B.x-P.x)*(A.y-P.y);
}
void Graham_scam()
{sort(V+2,V+n+1,compar);
 S.push_back(V[1]);
 S.push_back(V[2]);
 for(int i=3;i<=n;)
     {while(Cross_prod(S[S.size()-1],S[S.size()-2],V[i])<=0 && S.size()>2)
             S.pop_back();
      S.push_back(V[i]);
      i++;
     }
}
void citire()
{int i,xmin=INT_MAX,ymin=INT_MAX,poz;
 fin>>n;
 for(i=1;i<=n;i++)
     {fin>>V[i].x>>V[i].y;
      if(xmin>V[i].x || (xmin==V[i].x && ymin<V[i].y))
         {xmin=V[i].x;
          ymin=V[i].y;
          poz=i;
         }
     }
 swap(V[poz],V[1]);
}
void afisare()
{int i;
 fout<<S.size()<<'\n';
 for(i=0;i<S.size();i++)
     fout<<fixed<<setprecision(7)<<S[i].x<<' '<<S[i].y<<'\n';
}