#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 calc(punct a,punct b,punct c)
{
    return (b.y-a.y)*(c.x-a.x)<=(c.y-a.y)*(b.x-a.x);
}

inline bool cmp(const punct &a,const punct &b)
{
    return calc(v[1],a,b);
}

int main()
{
    int n,i,vf;
    f>>n;
    for(i=1;i<=n;i++)
        f>>v[i].x>>v[i].y;
    for(i=1;i<=n;i++)
    if(v[i].x<v[1].x||(v[i].x==v[1].x&&v[i].y<v[1].y))
        swap(v[1],v[i]);
    sort(v+2,v+n+1,cmp);
    st[1]=1;
    vf=1;
    for(i=2;i<=n;i++)
    {
        while(vf>1&&calc(v[st[vf-1]],v[i],v[st[vf]])==1)
            vf--;
        st[++vf]=i;
    }
    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;
}