#include<fstream>

#include<algorithm>

#include<iomanip>

using namespace std;

ifstream f("infasuratoare.in");

ofstream g("infasuratoare.out");

int st[120002];

bool viz[120002];



struct punct

{

    long double x,y;

};

punct v[120002];



inline bool cmp(const punct &a,const punct &b)

{

    if(a.x==b.x)

        return a.y<b.y;

    return a.x<b.x;

}



inline bool calc(punct a,punct b,punct c)

{

    return (c.y-a.y)*(b.x-a.x)<=(b.y-a.y)*(c.x-a.x);

}



int main()

{

    int n,i,vf,pas;

    f>>n;

    for(i=1;i<=n;i++)

        f>>v[i].x>>v[i].y;

    sort(v+1,v+n+1,cmp);

    st[1]=1;

    st[2]=2;

    vf=2;

    viz[2]=1;

    i=3;

    pas=1;

    while(viz[1]==0)

    {

        if(viz[i]==0)

        {

            while(vf>1&&calc(v[st[vf-1]],v[st[vf]],v[i])==1)

                viz[st[vf]]=0,vf--;

            st[++vf]=i;

            viz[i]=1;

        }

        if(i==n)

            pas=-1;

        i+=pas;

    }

    vf--;

    g<<vf<<'\n';

    for(i=1;i<=vf;i++)

        g<<fixed<<setprecision(12)<<v[st[i]].x<<" "<<fixed<<setprecision(12)<<v[st[i]].y<<'\n';

    return 0;

}