#include<fstream>
#include<cstdio>
#include<algorithm>
#include<iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
int n,i,vf,poz;
struct punct{double x,y;};
punct mini,v[120009],st[120009];
int sarus(punct a,punct b,punct c)
{
    return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);
}
bool cmp(punct a,punct b)
{
    return sarus(v[1],a,b)<0;
}
int main()
{
    f>>n;
    for(i=1;i<=n;++i)
    {
        f>>v[i].x>>v[i].y;
    }
    poz=1;
    for(i=2;i<=n;++i)
    {
        if(v[poz].x>v[i].x||v[poz].x==v[i].x&&v[poz].y>v[i].y)
        poz=i;
    }
    swap(v[1],v[poz]);
    sort(v+2,v+n+1,cmp);
    st[1]=v[1];
    st[2]=v[2];
    vf=2;
    for(i=3;i<=n;++i)
    {
        while(vf>=2&&sarus(st[vf-1],st[vf],v[i])>0)
        --vf;
        ++vf;
        st[vf]=v[i];
    }
    g<<vf<<'\n';
    for(i=vf;i;--i)
    g<<setprecision(9)<<st[i].x<<' '<<st[i].y<<'\n';
    return 0;
}