#include <stdio.h>
#include <algorithm>
#define NM 120005

using namespace std;

FILE *f=fopen("infasuratoare.in","r");
FILE *g=fopen("infasuratoare.out","w");

struct p{double x;double y;};

int i,N,k(1),u(2);
p A0,v[NM],st[NM];

bool cmp(p a,p b)
{
    return (A0.x-b.x)*(A0.y-a.y)<(A0.y-b.y)*(A0.x-a.x);
}

bool ung(p i,p j,p k)
{
    return i.x*j.y+j.x*k.y+k.x*i.y-i.x*k.y-j.x*i.y-k.x*j.y>0;
}

int main()
{
    fscanf(f,"%d",&N);
    for(i=1;i<=N;i++)
     fscanf(f,"%lf%lf",&v[i].x,&v[i].y);
    A0.x=v[1].x; A0.y=v[1].y;
    for(i=2;i<=N;i++)
     if(v[i].x<A0.x||(v[i].x==A0.x&&v[i].y<A0.y)) {A0=v[i]; k=i;}
    swap(v[1],v[k]); stable_sort(v+2,v+N+1,cmp);
    st[1]=v[1]; st[2]=v[2];
    for(i=3;i<=N;i++)
    {
        while(!ung(st[u-1],st[u],v[i])) u--;
        st[++u]=v[i];
    }
    fprintf(g,"%d\n",u);
    for(i=1;i<=u;i++)
     fprintf(g,"%lf %lf\n",st[i].x,st[i].y);
    return 0;
}