#include <fstream>
#include<algorithm>
#include<iomanip>

using namespace std;
ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");
struct ura {
    double x,y;
    int parte;
}v[120001],a,b;

bool cmp(ura a , ura b){
    if(a.x<b.x)
        return true;
    if(a.x>b.x)
        return false;
    if (a.y < b.y)
        return true;
    return false;
}
int st[120001];
double arie(ura a, ura b, ura c)
{
    return  a.x*b.y + b.x*c.y + c.x*a.y -b.y*c.x -c.y*a.x - a.y*b.x;
}
int main()
{
    int n,i,cop;
    int idx1=0,idx2=0,sp=1;
    fin >> n;
    for( i=1;i <= n; i++)
    {
        fin >> v[i].x >> v[i].y;
    }
    sort(v+1,v+n+1,cmp);
    a=v[1];
    b=v[n];
    for(i=2;i<=n-1;i++)
    {
        if(arie(a,b,v[i])<0)
            v[i].parte =1;
        else
            v[i].parte=2;
    }
    st[1]=1;
    for(i=2;i<=n;i++)
    {
        if(v[i].parte==1 || v[i].parte == 0)
        {
            while(sp>1 && arie(v[st[sp-1]], v[st[sp]],v[i])<0)
                sp--;
            st[++sp]=i;
        }
    }
    cop=sp;
    st[sp]=n;
    for(i=n-1;i>=1;i--)
    {
        if(v[i].parte==0 || v[i].parte==2)
        {
            while(sp> cop && arie(v[st[sp-1]], v[st[sp]], v[i])< 0)
                sp--;
            st[++sp]=i;
        }
    }
    fout << sp-1;
    fout << '\n';
    for(i=1;i<sp;i++)
        fout<<fixed<<setprecision(6)<<v[st[i]].x<<" "<<v[st[i]].y<<" "<<"\n";
    return 0;
}