/*
#include<stdio.h>
#include<algorithm>
#include<math.h>

using namespace std;

const int maxn = 120000;
const int INF = 1000000000;

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",ST[0] - 1);
	reverse(ST + 1, ST + ST[0] + 1);
	for(int i = 1;i < ST[0]; ++i)
	{
		printf("%lf %lf\n",X[ST[i]],Y[ST[i]]);
	}
	return 0;
}

*/

#include<stdio.h>
#include<algorithm>
#define Nmx 120001

int n,pzmin=1,nr;

struct coord
{
    double x,y;
}A[Nmx];
coord st[Nmx];

using namespace std;

void citire()
{
    scanf("%d",&n);
    for(int i=1;i<=n;++i)
        {
            scanf("%lf %lf",&A[i].x,&A[i].y);
            if(A[i].x<A[pzmin].x)
               pzmin=i;
             else if(A[i].x==A[pzmin].x)
                    if(A[i].y<A[pzmin].y)
                      pzmin=i;
        }
}

bool cmp(coord a,coord b)
{
    return (double)(a.x-A[1].x)*(b.y-A[1].y)<(double)(b.x-A[1].x)*(a.y-A[1].y);
}


long double semn(double xa,double ya,double xb,double yb,double xc,double yc)
{
    return (long double)xa*yb+xc*ya+xb*yc-xc*yb-xa*yc-ya*xb;
}

int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    citire();
    coord aux=A[1];
    A[1]=A[pzmin];
    A[pzmin]=aux;
    sort(A+2,A+n+1,cmp);
    st[++nr]=A[1];
    for(int i=2;i<=n;++i)
    {
        while(nr>=2&&semn(st[nr-1].x,st[nr-1].y,st[nr].x,st[nr].y,A[i].x,A[i].y)>0) nr--;
        st[++nr]=A[i];
    }
    printf("%d\n",nr);
    reverse(st+1,st+nr+1);
    for(int i=1;i<=nr;++i)
     printf("%.6lf %.6lf\n",st[i].x,st[i].y);
    return 0;
}