#include <fstream>
#include <iomanip>
#include <algorithm>
using namespace std;
ifstream f ("infasuratoare.in");
ofstream g ("infasuratoare.out");
const int nmax=12e4+3;
int n,t,sol[nmax],k;
struct usu
{
      double x,y;
}v[nmax];
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;
      t=1;
      for(int i=2;i<=n;++i)
      {
            f>>v[i].x>>v[i].y;
            if(v[i].x<v[t].x)
            {
                  t=i;
                  continue;
            }
            if(v[i].x==v[t].x&&v[i].y<v[t].y) t=i;
      }
      swap(v[1],v[t]);
      sort(v+2,v+n+1,cmp);
      sol[++k]=1;
      sol[++k]=2;
      for(int i=3;i<=n;++i)
      {
            while(k>1&&det({v[sol[k-1]].x,v[sol[k-1]].y},{v[sol[k]].x,v[sol[k]].y},{v[i].x,v[i].y})>0) --k;
            sol[++k]=i;
      }
      g<<k<<'\n';
      for(int i=1;i<=k;++i) g<<fixed<<setprecision(6)<<v[sol[i]].x<<' '<<v[sol[i]].y<<'\n';
      return 0;
}