#include <cstdio>
#define MaxN 10024

struct punct
{
      double x,y;
} a[MaxN],pct;

int s[MaxN],N,M,i,j=1;

void cit()
{
      freopen("infasuratoare.in","r",stdin);
      scanf("%lld",&N);
      scanf("%lf%lf",&a[1].x,&a[1].y); pct=a[1];
      for(i=2;i<=N;i++)
	{
		scanf("%lf%lf",&a[i].x,&a[i].y);
		if(a[i].y<pct.y || (a[i].y==pct.y && a[i].x<pct.x))
		{
			pct=a[i];
			j=i;
		}
	}
}


double prod(punct pct, punct a, punct b)
{
	return (a.x-pct.x)*(b.y-pct.y) - (b.x-pct.x)*(a.y-pct.y);
}

void swap(punct &x, punct &y)
{
	punct aux=x;
	x=y;
	y=aux;
}

void sort(punct arr[], int beg, int end)
{
	if(end>beg+1)
	{
		punct piv=arr[beg];
		int l=beg+1, r=end;
		while(l<r)
		{
			if(prod(pct,arr[l],piv)>0)
				  l++;
			else
				swap(arr[l], arr[--r]);
		}
		swap(arr[--l], arr[beg]);
		sort(arr, beg, l);
		sort(arr, r, end);
	}
}

void sol()
{
      punct aux=a[1];
	a[1]=a[j]; a[j]=aux;
	sort(a,2,N+1);
	M=2; s[1]=1; s[2]=2;
	for(i=3;i<=N;i++)
	{
		while(M>=2 && prod(a[s[M]],a[i],a[s[M-1]])<=0)
			M--;
		M++;
		s[M]=i;
	}
}

void afis()
{
      freopen("infasuratoare.out","w",stdout);
      printf("%d\n",M);
      for(i=1;i<=M;i++)
            printf("%lf %lf\n",a[s[i]].x,a[s[i]].y);
}

int main()
{
	cit();
      sol();
	afis();
	return 0;
}