#include <fstream>
#define N 120002
#include <algorithm>
#include <bitset>
#include <iomanip>

using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");

bitset <N> viz;
int who[N];
struct bla
{
    long double x,y;
}v[N];
bool cmp(bla A, bla B)
{
    if(A.x!=B.x) return A.x<B.x;
    return A.y<B.y;
}

long double det(int a, int b, int c)
{
    long double x1=v[a].x,x2=v[b].x,x3=v[c].x,y1=v[a].y,y2=v[b].y,y3=v[c].y;
    long double d;
    d=(x1*y2+x2*y3+x3*y1-x3*y2-x1*y3-x2*y1);
    return d;
}
int main()
{
    int n,nr=1,i,ss=2;
    f>>n;
    for(int i=1;i<=n;++i) f>>v[i].x>>v[i].y;
    sort(v+1,v+n+1,cmp);
    who[1]=1;
    who[2]=2,viz[2]=1;
    i=3;
    while(!viz[1])
    {
        while(viz[i])
        {
            if(i==n) nr=-1;
            i+=nr;
        }
        while(ss>=2 && det(who[ss-1],who[ss],i)<0)
            viz[who[ss]]=0,--ss;
        who[++ss]=i;
        viz[who[ss]]=1;
    }
    g<<ss-1<<'\n';
    for(int i=2;i<=ss;++i)
    {
        g<<fixed<<setprecision(15)<<v[who[i]].x<<' ';
        g<<fixed<<setprecision(15)<<v[who[i]].y<<'\n';
    }
    f.close();
    g.close();
    return 0;
}