#include<cstdio>
#include<vector>
#include<algorithm>
#include<cmath>
#define eps 1.e-12
using namespace std;

struct st
{
    double x,y;
};
st s[120005],aux;
int v[120005];
int ccw(st a,st b,st c)
{
    double cp;
    cp=(b.x-a.x)*(c.y-b.y)-(b.y-a.y)*(c.x-b.x);
    if(fabs(cp)<eps)
        return 0;
    if(cp>=eps)
        return 1;
    return -1;
}

bool cmp(st x,st y)
{
    return ccw(s[0],x,y)>eps;
}

int main()
{

    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    int n,i,top;
    scanf("%d",&n);
    scanf("%lf%lf",&s[0].x,&s[0].y);
    for(i=1;i<n;i++)
        {
            scanf("%lf%lf",&s[i].x,&s[i].y);
            if((s[i].y-s[0].y)<-eps)
                {
                aux=s[0];
                s[0]=s[i];
                s[i]=aux;
                }
            else
            if(fabs(s[i].y-s[i].x)<eps)
                {
                    if(s[i].x-s[0].x<-eps)
                    {
                        aux=s[0];
                        s[0]=s[i];
                        s[i]=aux;
                    }
                }
        }
    sort(s+1,s+n,cmp);
    v[0]=0;
    v[1]=1;
    s[n]=s[0];
    top=1;
    i=2;
    while(i<=n)
    {
        if(ccw(s[v[top-1]],s[v[top]],s[i])>0)
            {v[++top]=i;i++;}
        else
            top--;
    }
    printf("%d\n",top);
    for(i=0;i<top;i++)
        printf("%.6lf %.6lf\n",s[v[i]].x,s[v[i]].y);
    return 0;
}