#include<cstdio>
#include<cstring>
#include<algorithm>
#include<vector>
#define maxn 120010
#define inf 1<<30

using namespace std;
double X[maxn],Y[maxn];
int n,pi;
double xpi,ypi;
int IND[maxn];
int ST[maxn];

bool cmp(int i,int j)
{
	return ((double)((Y[i]-Y[pi])*(X[j]-X[pi]))> ((double)((X[i]-X[pi])*(Y[j]-Y[pi]))));

}
long double semn(int i1,int i2,int i3)
{
	 return (long double)(X[i1]*Y[i2]+X[i2]*Y[i3]+X[i3]*Y[i1]-X[i3]*Y[i2]-X[i1]*Y[i3]-X[i2]*Y[i1]);
}
void read()
{
	freopen("infasuratoare.in","r",stdin);
	scanf("%d",&n);
	pi=0;
	X[0]=inf,Y[0]=inf;
	for(int i=1;i<=n;i++)
	{
		scanf("%lf %lf",&X[i],&Y[i]);
		if(X[i]<X[pi] || ( X[i]==X[pi] && Y[i]<Y[pi])) pi=i;
	}
	for(int i=1;i<=n;i++)
	{
		if(i==pi) continue;
		IND[++IND[0]]=i;
	}
}

void solve()
{
	sort(IND+1,IND+IND[0]+1,cmp);
	ST[++ST[0]]=pi;
	for(int i=1;i<=IND[0];i++)
	{
		if(IND[i]==pi) continue;
		while(ST[0]>2 && semn(ST[ST[0]-1],ST[ST[0]],IND[i])>0)
		 ST[0]--;
		ST[++ST[0]]=IND[i];
	}
}

int main()
{
	read();
	freopen("infasuratoare.out","w",stdout);
	solve();
	printf("%d\n",ST[0]);
	for(int i=ST[0];i>=1;i--)
		printf("%lf %lf\n",X[ST[i]],Y[ST[i]]);
}