#include <cstdio>
#include <algorithm>
#define nmax 120005
#define punct pair <double,double>
#define x first
#define y second

using namespace std;

int n,vf;
punct p[nmax];
int st[nmax];
bool viz[nmax];
double eps=10e-12;

double det(punct a,punct b,punct c)
{
    return (a.x*b.y+b.x*c.y+c.x*a.y)-(a.y*b.x+b.y*c.x+a.x*c.y);
}

void citire()
{
    double ax,ay;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%lf%lf",&ax,&ay);
        p[i]=make_pair(ax,ay);
    }
}

void rezolv()
{
    st[1]=1;
    st[2]=2;
    vf=2;
    viz[1]=viz[2]=1;
    for(int i=3;i<=n;i++)
    {
        while(vf>1&&det(p[st[vf-1]],p[st[vf]],p[i])<eps)
            viz[st[vf--]]=0;
        viz[i]=1;
        st[++vf]=i;
    }
    for(int i=n-1;i>1;i--)
    {
        if(viz[i]==0)
        {
            while(vf>1&&det(p[st[vf-1]],p[st[vf]],p[i])<eps)
                viz[st[vf--]]=0;
            viz[i]=1;
            st[++vf]=i;
        }
    }
    while(vf>1&&det(p[st[vf-1]],p[st[vf]],p[1])<eps)
        vf--;
}

void afisare()
{
    printf("%d\n",vf);
    for(int i=1;i<=vf;i++)
        printf("%lf %lf\n",p[st[i]].x,p[st[i]].y);
}

int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    citire();
    sort(p+1,p+n+1);
    rezolv();
    afisare();
    return 0;
}