#include<stdio.h>
#include<algorithm>
#include<math.h>

using namespace std;

const int maxn = 1200000;
const int INF = 100000000;

double X[maxn],Y[maxn];
double V[maxn],ARIE;
int IND[maxn],N,ST[maxn];

bool cmpf(int i,int j)
{
	return V[i] < V[j];
}

double semn(int i1,int i2,int i3)
{
	return X[i1] * Y[i2] + X[i2] * Y[i3] + X[i3] * Y[i1] - Y[i1] * X[i2] - Y[i2] * X[i3] - Y[i3] * X[i1];
}

int main()
{
	freopen("grader_test6.in","r",stdin);
	freopen("grader_test6.ok","w",stdout);
	scanf("%d\n",&N);
	X[0] = INF;Y[0] = INF;
	int punct_initial = 0;
	for(int i = 1;i <= N; ++i)
	{
		scanf("%lf %lf",&X[i],&Y[i]);
		if (X[i] < X[punct_initial] || (X[i] == X[punct_initial] && Y[i] < Y[punct_initial])) punct_initial = i;
	}
	for(int i = 1;i <= N; ++i)
	{
		IND[i] = i;
		V[i] = atan2((X[i] - X[punct_initial]),(Y[i] - Y[punct_initial]));
	}
	V[punct_initial] = 0;
	sort(IND + 1,IND + N + 1,cmpf);
	ST[ST[0] = 1] = punct_initial;
	for(int i = 1;i <= N; ++i)
	{
		if (IND[i] == punct_initial) continue;
		while(ST[0] >= 2 && semn(ST[ST[0] - 1],ST[ST[0]],IND[i]) > 0) --ST[0];
		ST[++ST[0]] = IND[i];
	}
	ST[++ST[0]] = punct_initial;
	printf("%d\n",ST[0] - 1);
	for(int i = 1;i < ST[0]; ++i)
	{
		printf("%lf %lf\n",X[ST[i]],Y[ST[i]]);
	}
	return 0;
}