#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f ("infasuratoare.in");
ofstream g ("infasuratoare.out");
struct usu
{
      double x,y;
}v[120003];
int n,mc,sol[120003],k;
double det(const usu &t1,const usu &t2,const usu &t3)
{
      return t1.x*t2.y+t2.x*t3.y+t3.x*t1.y-t2.y*t3.x-t3.y*t1.x-t1.y*t2.x;
}
inline bool cmp(const usu &t1,const usu &t2)
{
      return det({v[1].x,v[1].y},t1,t2)<0;
}
int main()
{
      f>>n;
      f>>v[1].x>>v[1].y;
      mc=1;
      for(int i=2;i<=n;++i)
      {
            f>>v[i].x>>v[i].y;
            if(v[i].x<v[mc].x)
            {
                  mc=i;
                  continue;
            }
            if(v[i].x==v[mc].x&&v[i].y<v[mc].y) mc=i;
      }
      swap(v[1],v[mc]);
      sort(v+2,v+n+1,cmp);
      sol[++k]=1;
      sol[++k]=2;
      for(int i=3;i<=n;++i)
      {
            while(k>2&&det(v[sol[k-1]],v[sol[k]],v[i])>0) --k;
            sol[++k]=i;
      }
      g<<k<<'\n';
      for(int i=k;i>=1;--i) g<<fixed<<setprecision(6)<<v[sol[i]].x<<' '<<v[sol[i]].y<<'\n';
      return 0;
}