#include<stdio.h>
#include<vector>
#include<math.h>
#include <algorithm>
#define pb push_back

const int MAX = 120000;
const int INF = 1000000000;

using namespace std;

vector<int> convexH;
double X[MAX], Y[MAX];
int N, viz[MAX];

int main()
{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	
	int punct_initial = 0;
	int crt = 0;
	int move = 1;
	double last = 0;
	
	scanf("%d\n", &N);
	X[0] = Y[0] = INF;
	
	for(int i = 1; i <= N; ++i)
		scanf("%lf %lf\n", &X[i], &Y[i]);
		
	for(int i = 1; i <= N; ++i)
		if (X[i] < X[punct_initial]) punct_initial = i;
	
	crt = punct_initial;
	
	while(move || punct_initial != crt)
	{
		move = 0;
		convexH.pb(crt);
		double ma = 10000;
		int poznoua = crt;
		
		for(int i = 1; i <= N; ++i)
		{
			if (viz[i] || i == crt) continue;
			double unghi = atan2((X[i] - X[crt]), Y[i] - Y[crt]);			
			if (unghi < 0) unghi += 2* M_PI;
			unghi -= last;
			if (unghi < 0) unghi += 2 * M_PI;
			if (ma > unghi) {ma = unghi; poznoua = i;}
		}
		
		last = atan2(-(X[crt] - X[poznoua]), -(Y[crt] - Y[poznoua]));
		if (last < 0) last += 2 * M_PI;
		crt = poznoua;
		viz[crt] = 1;
	}
	
	reverse(convexH.begin(), convexH.end());
	printf("%d\n", convexH.size());
	
	for(unsigned int i = 0; i < convexH.size(); ++i)
		printf("%lf %lf\n", X[convexH[i]], Y[convexH[i]]);
	
	return 0;
}