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