#include <iostream>
#include <fstream>
#include <cmath>
#include <algorithm>
#include <iomanip>

using namespace std;

int n,last2,last1,S[120010],K;
double Z,minx=2000000000,miny=2000000000,ma,ta;
struct kt{
double x,y,tg;
};
kt v[120010];
int cmp(kt pp, kt qq)
{
    return pp.tg>qq.tg;
}
int main()
{
    int i,j;
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    cin>>n;
    for(i=1;i<=n;i++)
    {
        cin>>v[i].x>>v[i].y;
        if(minx>v[i].x)
        {
            minx=v[i].x;
            miny=v[i].y;
            j=i;
        }
        else if(minx==v[i].x)
            if(miny>v[i].y)
            {
                miny=v[i].y;
                j=i;
            }
    }
    v[j]=v[n];
    //n--;

    for(i=1;i<n;i++)
    {
        v[i].x-=minx;
        v[i].y-=miny;
        v[i].tg=atan2(v[i].y,v[i].x);
    }
    sort(v+1,v+n,cmp);
    v[0].x=0;
    v[0].y=0;
    K=2;
    S[1]=0;
    S[2]=1;
    for(i=2;i<n;i++)
    {
        while((v[S[K-1]].x*v[i].y+v[i].x*v[S[K]].y+v[S[K]].x*v[S[K-1]].y-
        v[S[K-1]].y*v[i].x-v[i].y*v[S[K]].x-v[S[K]].y*v[S[K-1]].x)<0)
            K--;
        K++;
        S[K]=i;
    }
    cout<<K<<"\n";
    for(i=K;i>=1;i--)
        v[S[i]].x+=minx,v[S[i]].y+=miny;
    std::cout.precision(10);
    for(i=K;i>=1;i--)
        cout<<v[S[i]].x<<" "<<v[S[i]].y<<'\n';
    return 0;
}