#include <cstdio>
#include <cmath>
#include <algorithm>

using namespace std;

const double eps=1.e-12;

struct point
{
	double x, y;
};

point p[120005], ll;
int st[120005];

int ccw(point a, point b, point c)
{
    double val=(b.x-a.x)*(c.y-b.y)-(b.y-a.y)*(c.x-b.x);
    if(val>=eps)return 1;
    if(val<=-eps)return -1;
    return 0;
}

bool cmp(point a, point b)
{
	return ccw(ll, a, b)>0;
}

int main()
{
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);
    int n;
    double tx, ty;
    scanf("%d%lf%lf", &n, &tx, &ty);
    ll.x=tx;ll.y=ty;
    for(int i=1;i<n;i++)
	{
		scanf("%lf%lf", &tx, &ty);
		p[i].x=tx;p[i].y=ty;
		if(ty-ll.y<=-eps || (fabs(ty-ll.y)<eps && tx-ll.x<=-eps))
		{
			double aux=ll.x;
			ll.x=p[i].x;
			p[i].x=aux;
			aux=ll.y;
			ll.y=p[i].y;
			p[i].y=aux;
		}
	}
	p[0]=ll;
	sort(p+1, p+n, cmp);
	p[n]=p[0];
	st[0]=0;st[1]=1;
	int top=1, i=2;
	while(i<=n)
	{
		if(ccw(p[st[top-1]], p[st[top]], p[i])>0)
		{
			st[++top]=i;
			i++;
		}
		else --top;
	}
	printf("%d\n", top);
	for(int i=0;i<top;i++)
		printf("%lf %lf\n", p[st[i]].x, p[st[i]].y);
    return 0;
}