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

using namespace std;

ifstream cin("infasuratoare.in");
ofstream cout("infasuratoare.out");

struct punct
{
    double long x,y;
}v[120005];

bool cmp(punct a,punct b)
{
    if (a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}

vector <punct> st;
punct rasp[120005];

int arie(punct a, punct b, punct c)
{
    return a.x*(b.y-c.y)+b.x*(c.y-a.y)+c.x*(a.y-b.y);
}

int main()
{
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>v[i].x>>v[i].y;
    long double S=0;
    sort(v+1,v+n+1, cmp);
    punct zero;
    zero.x=0;
    zero.y=0;
    st.push_back(zero);
    st.push_back(v[1]);
    int k=1;
    for(int i=2;i<=n;i++)
    {
        if(k>=2)
        {
            long double s=arie(st[k-1], st[k], v[i]);
            while(s<0 && k>=2)
            {
                st.pop_back();
                k--;
                s=arie(st[k-1], st[k], v[i]);
            }
        }
        st.push_back(v[i]);
        k++;
    }
    for(int i=1;i<=k;i++)
        rasp[i]=st[i];

    st.clear();
    int ck=k;
    k=1;
    st.push_back(zero);
    st.push_back(v[1]);
    for(int i=2;i<=n;i++)
    {
        if(k>=2)
        {
            long double s=st[k-1].x*(st[k].y-v[i].y)+st[k].x*(v[i].y-st[k-1].y)+v[i].x*(st[k-1].y-st[k].y);
            while(s>0 && k>=2)
            {
                st.pop_back();
                k--;
                s=st[k-1].x*(st[k].y-v[i].y)+st[k].x*(v[i].y-st[k-1].y)+v[i].x*(st[k-1].y-st[k].y);
            }
        }
        st.push_back(v[i]);
        k++;
    }
    cout<<ck+k-2<<'\n';
    for(int i=1;i<ck;i++)
        cout<<fixed<<setprecision(12)<<rasp[i].x<<" "<<rasp[i].y<<'\n';
    for(int i=k;i>=2;i--)
        cout<<fixed<<setprecision(12)<<st[i].x<<" "<<st[i].y<<'\n';
    return 0;
}