#include <fstream>
#include <iostream>
#include <string>
#include <complex>
#include <cmath>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <stack>
#include <algorithm>
#include <list>
#include <bitset>
#include <ctime>
#include <climits>
#include <cassert>
#include <iomanip>

using namespace std;


const string file = "algsort";
const string inputF = file + ".in";
const string outputF = file + ".out";

const double epsilon = 1e-7;
#define LL long long
#define ULL unsigned long long 
#define MOD1 666013
#define MOD2 666019
#define MOD3 1999999973
#define base 73

typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<string> vs;
typedef pair<int, int> ii;
typedef pair<long long, long long> ll;
typedef pair<double, double> dd;
typedef vector<ii> vii;
typedef vector<ll> vll;
typedef vector<dd> vdd;

#define all(V) V.begin(), V.end()
#define allr(V) V.rbegin(), V.rend()
#define for_c_it(container, it) for (auto it : container)
#define present(container, element) (container.find(element) != container.end()) 
#define sz(a) int((a).size()) 
#define pb push_back 
#define mp make_pair
#define zeroes(x) ((x ^ (x - 1)) & x)
#define maxn 200001

vdd V, st;
int N;

double crossProduct(const dd &A, const dd &B, const dd &C) {
	return (B.first - A.first) * (C.second - A.second) - (B.second - A.second) * (C.first - A.first);
}

bool cmp(const dd &p1,const dd &p2) {
	return crossProduct(V[0], p1, p2) < 0;
}

int convexHull() {
	int top, i;
	st[0] = V[0];
	st[1] = V[1];
 	top = 1;
	for (i = 2; i < N; ++i) {
		while (top >= 1 && crossProduct(st[top - 1], st[top], V[i]) > 0) {
			--top;
		}
		++top;
		st[top] = V[i];
	}
	
	return top;
}

int main() {
#ifndef INFOARENA
	freopen("input.txt", "r", stdin);
#else 
	freopen(inputF.c_str(), "r", stdin);
	freopen(outputF.c_str(), "w", stdout);
#endif
	int i, top;
	scanf("%d", &N);
	V.resize(N);
	st.resize(N);
	for (auto &x: V) {
		scanf("%lf %lf", &x.first, &x.second);
	}
	
	int pos = 0;
	for (i = 1; i < N; ++i) {
		if (V[i] < V[pos]) {
			pos = i;
		}
	}
	swap(V[0], V[pos]);
	sort(V.begin() + 1, V.end(), cmp);
		
	top = convexHull();
		
	printf("%d\n", top + 1);
	while(top >= 0) {
		printf("%.9lf %.9lf\n", st[top].first, st[top].second);
		--top;
	}

	return 0;
}