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

using namespace std;

const int MAX = 100002;
const int INF = 1000000000;

double X[MAX],Y[MAX];
long double V[MAX];
int pctInitial, N;
int indice[MAX], stiva[MAX];

bool comp(int i,int j)
{
	return (double)(X[i] - X[pctInitial]) * (Y[j] - Y[pctInitial]) < (double)(X[j] - X[pctInitial]) * (Y[i] - Y[pctInitial]);
}

long double semn(int i1,int i2,int i3)
{
	return (long double)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("infasuratoare.in", "r", stdin);
	freopen("infasuratoare.out", "w", stdout);
	
	X[0] = INF;
	Y[0] = INF;
	int punct_initial = 0;
	
	scanf("%d\n",&N);
	
	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;
	}
	
	pctInitial = punct_initial;
	for(int i = 1;i <= N; ++i)
	{
		if (i == punct_initial) continue; 
		indice[++indice[0]] = i;
	}
	
	sort(indice + 1,indice + indice[0] + 1,comp);
	
	stiva[stiva[0] = 1] = punct_initial;
	
	for(int i = 1; i <= indice[0]; ++i)
	{
		if (indice[i] == punct_initial) continue;
		while(stiva[0] >= 2 && semn(stiva[stiva[0] - 1], stiva[stiva[0]], indice[i]) > 0) --stiva[0];
		stiva[++stiva[0]] = indice[i];
	}
	
	stiva[++stiva[0]] = punct_initial;
	printf("%d\n",stiva[0] - 1);
	
	reverse(stiva + 1, stiva + stiva[0] + 1);
	
	for(int i = 1;i < stiva[0]; ++i)
	{
		printf("%lf %lf\n", X[stiva[i]], Y[stiva[i]]);
	}
	return 0;
}