#include <stdio.h>
#include <math.h>
#include <algorithm>
#define NM 120005
#define mxy 1000000001

using namespace std;

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

struct p{double x;double y;};

int i,N;
p A0,v[NM],st[NM];

double d(p i,p j)
{
    return sqrt((i.x-j.x)*(i.x-j.x)+(i.y-j.y)*(i.y-j.y));
}

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;
}

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

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; int pos(1);
    for(i=2;i<=N;i++)
     if(v[i].x<A0.x) {pos=i; A0=v[i];}
     else if(v[i].x==A0.x&&v[i].y<A0.y) {pos=i; A0=v[i];}
    swap(v[1],v[pos]);
    stable_sort(v+2,v+N+1,cmp);
    st[1]=v[1];
    st[2]=v[2];
    int u(2);
    for(i=3;i<=N;i++)
    {
        while(u>=2&&!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,"%f %f\n",st[i].x,st[i].y);
    return 0;
}