#include <cstdio>
#include <algorithm>
using namespace std;

const int MAX_N = 120010;

#define x first
#define y second
#define pd pair<double, double>

int n;
pd a[MAX_N];
int s[MAX_N], f[MAX_N];

int sign(pd a, pd b, pd c)
{
	return 1 - ((a.x - c.x) * (b.y - c.y) - (b.x - c.x) * (a.y - c.y) <= 0);
}

int main()
{
	int i, p;
	freopen("infasuratoare.in", "r", stdin);

	freopen("infasuratoare.out", "w", stdout);

	scanf("%d", &n);

	for (i = 1; i <= n; ++i)
		scanf("%lf %lf", &a[i].x, &a[i].y);

	sort(a + 1, a + n + 1);

	s[s[0] = 1] = 1;
	for (i = 2, p = 1; i; i += (p = (i == n) ? -p : p))
	{
		if (!f[i])
		{
			while (s[0] > 1 && sign(a[i], a[s[s[0]]], a[s[s[0] - 1]]))
				f[s[s[0]--]] = 0;

			f[s[++s[0]] = i] = 1;
		}
	}

	printf("%d\n", s[0] - 1);
	
	for (i = 1; i < s[0]; ++i)
		printf("%.6f %.6f\n", a[s[i]].x, a[s[i]].y);
}