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

struct cmp {
    bool operator ()(pair<double,double> a, pair<double,double> 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);

    int pmin = 1;
    for(int i = 2; i <= n; ++i)
        if(v[i] < v[pmin])
            pmin = i;

    swap(v[1],v[pmin]);

    sort(v+2,v+n+1,Cmp);

    for(int i = 1; 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;
}