#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ar array
#define vt vector
#define pq priority_queue
#define pu push
#define pub push_back
#define em emplace
#define emb emplace_back

#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define allp(x, l, r) x.begin() + l, x.begin() + r
#define len(x) (int)x.size()

using namespace std;
using namespace __gnu_pbds;

using ll = long long;
using ld = long double;
using ull = unsigned long long;

template <class T, size_t N>
void re(array <T, N>& x);
template <class T> 
void re(vt <T>& x);

template <class T> 
void re(T& x) {
    cin >> x;
}

template <class T, class... M> 
void re(T& x, M&... args) {
    re(x); re(args...);
}

template <class T> 
void re(vt <T>& x) {
    for(auto& it : x)
        re(it);
}

template <class T, size_t N>
void re(array <T, N>& x) {
    for(auto& it : x)
        re(it);
}

template <class T, size_t N>
void wr(array <T, N> x);
template <class T> 
void wr(vt <T> x);

template <class T> 
void wr(T x) {
    cout << x;
}

template <class T, class ...M>  void wr(T x, M... args) {
    wr(x), wr(args...);
}

template <class T> 
void wr(vt <T> x) {
    for(auto it : x)
        wr(it, ' ');
}

template <class T, size_t N>
void wr(array <T, N> x) {
    for(auto it : x)
        wr(it, ' ');
}


inline void Open(const string Name) {
    #ifndef ONLINE_JUDGE
        (void)!freopen((Name + ".in").c_str(), "r", stdin);
        (void)!freopen((Name + ".out").c_str(), "w", stdout);
    #endif
}

struct PT {
    double x, y;
    PT() {
        x = y = 0;
    }

    PT(double x, double y) : x(x), y(y) {}
    PT(const PT& p) : x(p.x), y(p.y) {}
    PT operator + (const PT& a) const {
        return PT(x + a.x, y + a.y);
    }
    PT operator - (const PT& a) const {
        return PT(x - a.x, y - a.y);
    }
    PT operator * (const double a) const {
        return PT(x * a, y * a);
    }


    friend istream& operator>> (istream &stream, PT& a){
        stream >> a.x >> a.y;
        return stream;
    }
};

inline double dot(PT a, PT b) { 
    return a.x * b.x + a.y * b.y; 
}

inline double dist2(PT a, PT b) { 
    return dot(a - b, a - b); 
}

inline double cross(PT a, PT b) { 
    return a.x * b.y - a.y * b.x; 
}

int orientation(PT a, PT b, PT c) {
    double v = cross(b - a, c - a);
    if (v < 0) return -1; //clockwise
    if (v > 0) return +1; // counter-clockwise
    return 0;
}

bool cw(PT a, PT b, PT c, bool include_collinear) {
    int o = orientation(a, b, c);
    return o < 0 || (include_collinear && o == 0);
}

bool collinear(PT a, PT b, PT c) { 
    return orientation(a, b, c) == 0; 
}

void convex_hull(vt <PT>& a, bool include_collinear = false) {
    PT p0 = *min_element(a.begin(), a.end(), [](PT a, PT b) {
        return make_pair(a.y, a.x) < make_pair(b.y, b.x);
    });

    sort(all(a), [&p0](const PT& a, const PT& b) {
        int o = orientation(p0, a, b);
        if (o == 0)
            return dist2(p0, a) < dist2(p0, b);
        return o < 0;
    });

    if (include_collinear) {
        int i = len(a) - 1;
        while (i >= 0 && collinear(p0, a[i], a.back())) i--;
        reverse(a.begin() + i + 1, a.end());
    }

    vt <PT> st;
    for (int i = 0; i < len(a); ++i) {
        while (len(st) > 1 && !cw(st[len(st) - 2], st.back(), a[i], include_collinear)) {
            st.pop_back();
        }
        st.pub(a[i]);
    }

    a = st;
}

void solve() {
    int n; re(n);
    vt <PT> v(n); re(v);
    convex_hull(v, false);


    wr(len(v), '\n');
    cout << fixed << setprecision(12);
    for (int i = 0; i < len(v); ++i) {
        if (i == 0) wr(v[i].x, ' ', v[i].y, '\n');
        else wr(v[len(v) - i].x, ' ', v[len(v) - i].y, '\n');
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    Open("infasuratoare");

    int t = 1;
    for(;t;t--) {
        solve();
    }
    
    return 0;
}