#include <bits/stdc++.h>

using namespace std;

vector <int >st;
pair <double ,double >punc[120005];
int n;
void citire()
{
    scanf("%d",&n);
    for (int i=1;i<=n;++i)
        scanf("%lf%lf",&punc[i].first,&punc[i].second);
}
double det(pair <double,double > a,pair <double,double > b,pair <double ,double >c)
{
    return (b.first-a.first)*(c.second-a.second)-(b.second-a.second)*(c.first-a.first);
}
struct cmp{
    bool operator ()(pair <double,double > a,pair < double ,double > b)
    {
        return det(punc[1],a,b)>0;
    }
};
void sortare_trig()
{
    int p=1;
    for (int i=2;i<=n;++i)
        if (punc[i]<punc[p])
            p=i;
    swap(punc[1],punc[p]);
    sort(punc+2,punc+n+1,cmp());
}
void infasuratoare()
{
    sortare_trig();
    st.push_back(1);
    st.push_back(2);
    for (int i=3;i<=n;++i)
    {
        int siz=st.size();
        while (siz>=2 && det(punc[st[siz-2]],punc[st[siz-1]],punc[i])<0)
        {
            --siz;
            st.pop_back();
        }
        st.push_back(i);
    }
    int siz=st.size();
    printf("%d\n",siz);
    for (int i=0;i<siz;++i)
        printf("%lf %lf\n",punc[st[i]].first,punc[st[i]].second);
}
int main()
{
    freopen("infasuratoare.in","r",stdin);
    freopen("infasuratoare.out","w",stdout);
    citire();
    infasuratoare();
    return 0;
}