#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>

using namespace std;

#define x first
#define y second

typedef pair<double,double> Pair;

const int Nmax = 120011 ;

int N,Size;
Pair A[Nmax];
int St[Nmax],Rez[Nmax];

int Ecu ( Pair A , Pair B , Pair P )
{
	double a = A.y - B.y ; 
	double b = B.x - A.x ;
	double c = - A.y * B.x + B.y * A.x ;
	
	if ( a*P.x + b*P.y + c > 0 ) return 1;
	if ( a*P.x + b*P.y + c < 0 ) return -1;
	
	return 0;
}

#define EPS 1e-12

inline int cmp(double a, double b)
{
    if (a + EPS < b) return -1;
    if (b + EPS < a) return +1;
    return 0;
}

#undef EPS

int cmp_Pair(const Pair &a, const Pair& b)
{
    int r = cmp(a.x, b.x);
    if (r != 0) return r == -1;
    return cmp(a.y, b.y) == -1;
}

void Andrew()
{
	sort(A+1,A+N+1,cmp_Pair);
	
	St[++Size] = 1;
	for (int i=2;i<N;++i)
		if ( Ecu ( A[N] , A[1] , A[i] ) < 0 )
		{
			St[++Size] = i;
			if ( Size > 2 )
				while ( Size > 2 ) 
				{
					if ( Ecu ( A[St[Size-2]] , A[St[Size]] , A[St[Size-1]] ) <= 0 )
						St[Size-1]=St[Size],
						--Size,
						St[Size+1]=0;
					else
						break;
				}
		}
	for (int i=1;i<=Size;++i)
		Rez[++Rez[0]]=St[i],
		St[i]=0;
	
	Size=0;	
	St[++Size] = N;
	for (int i=N-1;i>1;--i)
		if ( Ecu ( A[1] , A[N] , A[i] ) < 0 )
		{
			St[++Size] = i;
			if ( Size > 2 )
				while ( Size > 2 ) 
				{
					if ( Ecu ( A[St[Size-2]] , A[St[Size]] , A[St[Size-1]] ) <= 0 )
						St[Size-1]=St[Size],
						--Size,
						St[Size+1]=0;
					else
						break;
				}
		}
	for (int i=1;i<=Size;++i)
		Rez[++Rez[0]]=St[i],
		St[i]=0;
}

ifstream F("infasuratoare.in");
ofstream G("infasuratoare.out");

int main()
{
	F>>N;
	for (int i=1;i<=N;++i)
		F>>A[i].x>>A[i].y;
	
	Andrew();
	
	G<<Rez[0]<<'\n';
	for (int i=Rez[0];i;--i)
		G<<fixed<<setprecision(6)<<A[Rez[i]].x<<' '<<A[Rez[i]].y<<'\n';
}