#include <iostream>
#include <iomanip>
#include <algorithm>
#include <assert.h>
#include <complex>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <tuple>
#include <cmath>
#include <bitset>
#include <cctype>
#include <set>
#include <map>
#include <unordered_map>
#include <numeric>
#include <functional>
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(ll i=ll(a);i<ll(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define rrep(i,a) for(ll i=ll(a-1);i>=0;--i)
#define all(x) (x).begin(),(x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(),(V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
inline void Yes(bool condition){ if(condition) PRINT("Yes"); else PRINT("No"); }
template<class itr> void cins(itr first,itr last){
    for (auto i = first;i != last;i++){
        cin >> (*i);
    }
}
template<class itr> void array_output(itr start,itr goal){
    string ans = "",k = " ";
    for (auto i = start;i != goal;i++) ans += to_string(*i)+k;
    if (!ans.empty()) ans.pop_back();
    PRINT(ans);
}
ll gcd(ll a, ll b) {
    return a ? gcd(b%a,a) : b;
}

const ll INF = 1e15;
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll EPS = 1e-10;
int sgn(const double a){
    return (a < -EPS ? -1 : (a > EPS ? +1 : 0));
}
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> tri;
typedef pair<double,double> point;
typedef complex<double> Point;
const ll MAX = 30000;
constexpr ll nx[8] = {1,0,-1,0,1,-1,1,-1};
constexpr ll ny[8] = {0,1,0,-1,1,1,-1,-1};

// complexをpair-likeに
bool complexSort(Point lhs,Point rhs){
    if (sgn(lhs.imag()-rhs.imag())){
        return lhs.imag() < rhs.imag();
    }
    else{
        return lhs.real() < rhs.real();
    }
}

double cross(Point z1,Point z2){
    return (conj(z1)*z2).imag();
}
//graham scan
vector<Point> convex_hull(vector<Point> p){
    sort(all(p),complexSort);
    int cnt = 0,n = p.size();
    vector<Point> s(n*2);
    rep(i,n){
        while (cnt > 1 && sgn(cross(s[cnt-1]-s[cnt-2],p[i]-s[cnt-1])) < 0) cnt--;
        s[cnt++] = p[i];
    }
    for (ll i = n-2,t = cnt;i >= 0;i--){
        while (cnt > t && sgn(cross(s[cnt-1]-s[cnt-2],p[i]-s[cnt-1])) < 0) cnt--;
        s[cnt++] = p[i];
    }
    s.resize(cnt-1);
    return s;
}

//caliper
double convex_diameter(vector<Point> p){
    int n = p.size();
    if (n == 2){
        return abs(p[0]-p[1]);
    }
    int i = 0,j = 0;
    rep(k,n){
        if (!complexSort(p[i],p[k])) i = k;
        if (complexSort(p[j],p[k])) j = k;
    }
    double res = 0;
    int si = i,sj = j;
    while (i != sj || j != si){
        chmax(res,abs(p[i]-p[j]));
        if (sgn(cross(p[(i+1)%n]-p[i],p[(j+1)%n]-p[j])) < 0){
            i = (i+1)%n;
        }
        else{
            j = (j+1)%n;
        }
    }
    return res;
}

int main(){
    //cin.tie(0);
    //ios::sync_with_stdio(false);
    ll n;
    cin >> n;
    vector<Point> p;
    double x,y;
    rep(i,n){
        cin >> x >> y;
        p.push_back(Point(x,y));
    }
    auto s = convex_hull(p);
    PRINT(s.size());
    vector<P> ans;
    for (auto z:s){
        ll a,b;
        a = round(z.real()),b = round(z.imag());
        cout << a << " " << b << endl;
    }
}



Measured memory_bytes: 9232