//horatiu11
# include <cstdio>
# include <algorithm>
# define nmax 120001
using namespace std;
int n,poz=1,size;
struct pct{double x,y;}a[nmax];
int st[nmax];
inline double det(pct A, pct B, pct C)
{
    return A.x*B.y+B.x*C.y+C.x*A.y-C.x*B.y-A.x*C.y-B.x*A.y;
}
inline bool cmp(pct A, pct B)
{
    double dy1=A.y-a[1].y,dy2=B.y-a[1].y,dx1=A.x-a[1].x,dx2=B.x-a[1].x;
    return (dy1*dx2<dx1*dy2);
}
inline void infasuratoare()
{
    int i;
    st[1]=1;st[2]=2;size=2;
    for(i=3;i<=n;++i)
    {
        while(size>=2 && det(a[st[size-1]],a[st[size]],a[i])<0)
            size--;
        st[++size]=i;
    }
    printf("%d\n",size);
    for(i=1;i<=size;++i)
        printf("%lf %lf\n",a[st[i]].x,a[st[i]].y);
}
int main()
{
    int i;
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;++i)
    {
        scanf("%lf%lf",&a[i].x,&a[i].y);
        if(a[i].x<a[poz].x)poz=i;
        else  if(a[i].x==a[poz].x && a[i].y<a[poz].y)poz=i;
    }
    swap(a[1],a[poz]);
    sort(a+2,a+n+1,cmp);
    infasuratoare();
    return 0;
}