#include<fstream>
#include<cmath>
#include<iomanip>
#include<algorithm>
#define NMAX 120010
#define EPS 0.00000000001

using namespace std;

struct punct
{
	double x, y;
	bool vz;
}a[NMAX];
int n, S[NMAX];

ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

void Citeste()
{
	int i;
	f>>n;
	for (i=1; i<=n; ++i)
		f>>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;
}*/

inline bool cmp(punct A, punct B)
{
	if (fabs(A.x-B.x)<EPS)
	if (A.y-B.y<EPS) return 1;
	else return 0;
	else if (A.x-B.x<EPS) return 1;
	else return 0;
}

double plan(punct A, punct B, punct C)
{
	return A.x*B.y+B.x*C.y+C.x*A.y-B.y*C.x-C.y*A.x-A.y*B.x;
}

void Solve()
{
	int i, m;
	double P;
	
	S[1]=1; S[2]=2; m=2;
	a[2].vz=1;
	for (i=3; i<=n; ++i)
	{
		P=plan(a[S[m-1]], a[S[m]], a[i]);
		while (P>0 && m>2) a[S[m]].vz=0, --m, P=plan(a[S[m-1]], a[S[m]], a[i]);
		if (P<0) S[++m]=i, a[i].vz=1;
	}
	
	for (i=n; i>0; --i)
		if (!a[i].vz)
		{
			P=plan(a[S[m-1]], a[S[m]], a[i]);
			while (P>0 && m>2) a[S[m]].vz=0, S[m]=0, --m, P=plan(a[S[m-1]], a[S[m]], a[i]);
			if (P<0) S[++m]=i, a[i].vz=1;	
		}
	g<<m-1<<"\n";
	for (i=m; i>1; --i)
		g<<fixed<<a[S[i]].x<<" "<<a[S[i]].y<<"\n";
}

int main()
{
	Citeste();
	sort(a+1, a+n+1, cmp);
	Solve();
	f.close();
	g.close();
	return 0;
}