#include <cstdio>
#include <algorithm>
#define nmax 120001

using namespace std;

struct punct{ double x,y;} a[nmax],pct;

int n,m,s[nmax];

double prod_vec(punct pct,punct A,punct B)
{
    return (A.x-pct.x)*(B.y-pct.y)-(B.x-pct.x)*(A.y-pct.y);
}

int cmp(punct A,punct B)
{
    return prod_vec(pct,A,B)>0;
}

int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    scanf("%d",&n);
    scanf("%lf %lf",&a[1].x,&a[1].y);
    pct=a[1];
    int j=1;
    for(int i=2;i<=n;++i)
    {
        scanf("%lf %lf",&a[i].x,&a[i].y);
        if(a[i].y<pct.y || (a[i].y==pct.y && a[i].x<pct.x))
        {
            pct=a[i];
            j=i;
        }
    }
    punct aux=a[1];
    a[1]=a[j];
    a[j]=aux;
    sort(a+2,a+n+1,cmp);
    m=2;
    s[1]=1;
    s[2]=2;
    for(int i=3;i<=n;++i)
    {
        while(m>=2 && prod_vec(a[s[m]],a[i],a[s[m-1]])<=0)
            m--;
        s[++m]=i;
    }
    printf("%d\n",m);
    for(int i=1;i<=m;++i)
      printf("%lf %lf\n",a[s[i]].x,a[s[i]].y);
    return 0;
}