#include <fstream>
#include <algorithm>
#include <vector>
#include <cstdio>
#include <cstring>
#include <math.h>

using namespace std;

const int NMAX = 120005;
const int INF = 0x3f3f3f3f;

double X[NMAX], Y[NMAX];
int init, ind[NMAX], stack[NMAX], n;

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

inline long double cross(int i, int j, int k)
{
	return (long double)X[i] * Y[j] + X[j] * Y[k] + X[k] * Y[i] - Y[i] * X[j] - Y[j] * X[k] - Y[k] * X[i];
}

int main()
{
	ifstream fin("infasuratoare.in");
	freopen("infasuratoare.out", "w", stdout);

	fin >> n;
	X[0] = INF, Y[0] = INF;
	int init_point = 0;

	for (int i = 1; i <= n; ++i) {
		fin >> X[i] >> Y[i];
		if (X[i] < X[init_point] || (X[i] == X[init_point] && Y[i] < Y[init_point]))
			init_point = i;
	}

	init = init_point;
	for (int i = 1; i <= n; ++i) {
		if (i == init_point)
			continue;
		ind[++ind[0]] = i;
	}
	
	sort(ind + 1, ind + ind[0] + 1, comp);
	stack[stack[0] = 1] = init_point;
	
	for (int i = 1; i <= ind[0]; ++i) {
		if (ind[i] != init_point)
		 	while (stack[0] >= 2 && cross(stack[stack[0] - 1], stack[stack[0]], ind[i]) > 0)
				--stack[0];
		stack[++stack[0]] = ind[i];
	}
	stack[++stack[0]] = init_point;
	
	printf("%d\n", stack[0] - 1);
	reverse(stack + 1, stack + stack[0] + 1);
	for (int i = 1; i < stack[0]; ++i) 
		printf("%lf %lf\n", X[stack[i]], Y[stack[i]]);
	return 0;
}