#include <bits/stdc++.h>

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

const int nmax =120003;

struct Punct
{
    double x,y;
};

int n;
Punct a[nmax];
int st[nmax],top,v[nmax];

double F(int i,int j , int p)
{  // determina semiplanul in care se afla p fata de dreapta i,j
    return a[p].x*( a[i].y-a[j].y )+a[p].y*(a[j].x-a[i].x)+a[i].x*a[j].y-a[j].x*a[i].y;
}

void Citire()
{
    int i;
    fin>>n;
    for(i=1;i<=n;++i)
        fin>>a[i].x>>a[i].y;

}


inline bool cmp(Punct A,Punct B)
{
    if(A.y==B.y)
        return A.x<B.x;
    return A.y<B.y;
}

void Hill() //alg lui Hill
{
    sort(a+1,a+n+1,cmp);
    st[++top]=1; v[2]=1;
    st[++top]=2;
    int i;
    for(i=3;i<=n;++i)
    {
          while( top>1 &&  F(st[top-1],st[top],i) <0)
          { v[st[top]]=0;
              top--;
          }
          st[++top]=i;
          v[i]=1;
    }

    for(i=n-1;i>=1;--i)
        if(v[i]==0)
    {
          while( top>1 &&  F(st[top-1],st[top],i) <0)
          { v[st[top]]=0;
              top--;
          }
          st[++top]=i;
          v[i]=1;
    }



}

void Afisare()
{
    int i;

    fout<<top-1<<"\n";
    for(i=1;i<top;++i)
        fout<<setprecision(12)<<fixed<<a[st[i]].x<<" "<<a[st[i]].y<<"\n";
}


int main()
{
    Citire();
    Hill();
    Afisare();


    return 0;
}