#include <cstdio>
#include <algorithm>
#include <stack>
#include <vector>
#define f first
#define s second
using namespace std;

const int nmx = 120002;

int n;
pair <double,double> v[nmx];
vector <int> st;

double determinant(pair<int,int> a, pair<int,int> b, pair<int,int> c){
    return ((b.f-a.f)*(c.s-a.s)) - ((c.f-a.f)*(b.s-a.s));
}

struct cmp{
    bool operator ()(pair<int,int> a, pair<int,int> b){
        return determinant(v[1],a,b) > 0;
    }
}Cmp;

int main(){
    freopen("infasuratoare.in", "r", stdin);
    freopen("infasuratoare.out", "w", stdout);

    scanf("%d", &n);
    for(int i = 1;i <= n; ++i)
        scanf("%lf %lf", &v[i].f, &v[i].s);

    st.push_back(1);
    st.push_back(2);
    sort(v+2,v+n+1,Cmp);

    for(int i = 3; i <= n; ++i){
        while(st.size() > 2 && determinant(v[st[st.size()-2]],v[st[st.size()-1]],v[i]) < 0)
             st.pop_back();
        st.push_back(i);
    }

    printf("%d\n", st.size());
    for(size_t i = 0; i < st.size(); ++i)
        printf("%lf %lf\n", v[st[i]].f, v[st[i]].s);

    return 0;
}