#include <bits/stdc++.h>

#define int long long

#define sz(a) int((a).size())
#define all(a) (a).begin(), (a).end()

#define lsb(x) (x & (-x))
#define vi vector<int>
#define YES { cout << "YES" << endl; return; }
#define NO { cout << "NO" << endl; return; }

using ll = long long;
using pii = std::pair<int, int>;
using pdd = std::pair<double, double>;

using namespace std;
ifstream fin ("infasuratoare.in");
ofstream fout ("infasuratoare.out");
double arie(pdd a, pdd b, pdd c){
    return  a.first*b.second + b.first*c.second + c.first*a.second -b.second*c.first -c.second*a.first - a.second*b.first;
}
ofstream&operator << (ofstream&iesire, pdd&a){
    iesire << a.first << " " << a.second << '\n';
    return iesire;
}
bool cmp(pdd a, pdd b){
    if (a.first != b.first)
        return a.first < b.first;

}
void solve_testcase() {
    int n;
    fin >> n;
    vector<pdd>p(n);
    vi tip(n, 0);
    for (auto &it : p)
        fin >> it.first >> it.second;
    sort(all(p));
    for (int i = 1; i < n - 1; ++i){
        if (arie(p[0], p.back(), p[i]) < 0)
            tip[i] = 1;
        if (arie(p.front(), p.back(), p[i]) > 0)
            tip[i] = 2;
    }
    vector<pdd> stk = {p.front()};
    for (int i = 1; i < n; ++i){
        if (tip[i] != 2){
            while (stk.size() > 1 && arie(stk[stk.size()], stk[stk.size() - 1], p[i]) < 0)
                   stk.pop_back();
            stk.push_back(p[i]);
        }
    }
    int csz = stk.size();
    for (int i = n - 2; i >= 0; --i){
        if (tip[i] != 1){
            while (stk.size() > csz && arie(stk[stk.size()], stk[stk.size() - 1], p[i]) < 0)
                   stk.pop_back();
            stk.push_back(p[i]);
        }
    }
    stk.pop_back();
    fout << stk.size() << '\n';
    fout << fixed << setprecision(6);
    for (auto &it : stk)
        fout << it;
}

signed main() {
    int t = 1;
    // cin >> t;
    while (t--)
        solve_testcase();
    return 0;
}