//sursa nu-mi apartine
//motiv: verificare dak e ok 
#include <cstdio>
#include <algorithm>
#include <cmath>
 
using namespace std;
 
const int maxn = 120000;
const int INF = 1000000001;
 
double X[maxn],Y[maxn];
//long double V[maxn];
int PI,IND[maxn],N,ST[maxn];
 
bool cmpf(int i,int j)
{
	return (double)(X[i] - X[PI]) * (Y[j] - Y[PI]) < (double)(X[j] - X[PI]) * (Y[i] - 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] - Y[i1] * X[i2] - Y[i2] * X[i3] - Y[i3] * X[i1];
}
 
int main()
{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	scanf("%d\n",&N);
	X[0] = INF;Y[0] = INF;
	int punct_initial = 0;
	for(int i = 1;i <= N; ++i)
	{
		scanf("%lf %lf",&X[i],&Y[i]);
		if (X[i] < X[punct_initial] || (X[i] == X[punct_initial] && Y[i] < Y[punct_initial])) punct_initial = i;
	}
	PI = punct_initial;
	for(int i = 1;i <= N; ++i)
	{
		if (i == punct_initial) continue;
		IND[++IND[0]] = i;
	}
	sort(IND + 1,IND + IND[0] + 1,cmpf);
	ST[ST[0] = 1] = punct_initial;
	for(int i = 1;i <= IND[0]; ++i)
	{
		if (IND[i] == punct_initial) continue;
		while(ST[0] >= 2 && semn(ST[ST[0] - 1],ST[ST[0]],IND[i]) > 0) --ST[0];
		ST[++ST[0]] = IND[i];
	}
	ST[++ST[0]] = punct_initial;
	//printf("%d\n",N - (int)(ST[0]-1));
	reverse(ST + 1, ST + ST[0] + 1);
	printf("%lf\n", ST[0] );
	for(int i = 1;i < ST[0]; ++i)
	{
		printf("%lf %lf\n",X[ST[i]],Y[ST[i]]);
	}
	return 0;
}