#define programstate2
#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ull unsigned ll
#define vec vector
#define flist forward_list
#define um unordered_map
#define us unordered_set
#define prioq priority_queue
#define all(x) x.begin(), x.end()
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define ld long double
#define cd complex<ld>
#define pll pair<ll, ll>
#define tll tuple<ll, ll, ll>
#define ass assign
#define fun function

#define LL_MAX LLONG_MAX
#define LL_MIN LLONG_MIN
#define ULL_MAX ULLONG_MAX
#define LD_MAX LDBL_MAX
#define LD_MIN LDBL_MIN

#define nl " \n"

#define vv(type, name, n, ...) vector<vector<type>> name(n, vector<type>(__VA_ARGS__))
#define vvv(type, name, n, m, ...) \
	vector<vector<vector<type>>> name(n, vector<vector<type>>(m, vector<type>(__VA_ARGS__)))

// https://trap.jp/post/1224/
#define rep1(n) for(ll i=0; i<(ll)(n); ++i)
#define rep2(i,n) for(ll i=0; i<(ll)(n); ++i)
#define rep3(i,a,b) for(ll i=(ll)(a); i<(ll)(b); ++i)
#define rep4(i,a,b,c) for(ll i=(ll)(a); i<(ll)(b); i+=(ll)(c))
#define cut4(a,b,c,d,e,...) e
#define rep(...) cut4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)
#define rep1e(n) for(ll i=1; i<=(ll)(n); ++i)
#define rep2e(i,n) for(ll i=1; i<=(ll)(n); ++i)
#define rep3e(i,a,b) for(ll i=(ll)(a); i<=(ll)(b); ++i)
#define rep4e(i,a,b,c) for(ll i=(ll)(a); i<=(ll)(b); i+=(ll)(c))
#define repe(...) cut4(__VA_ARGS__,rep4e,rep3e,rep2e,rep1e)(__VA_ARGS__)
#define per1(n) for(ll i=(ll)(n)-1; i>=0; --i)
#define per2(i,n) for(ll i=(ll)(n)-1; i>=0; --i)
#define per3(i,a,b) for(ll i=(ll)(a)-1; i>=(ll)(b); --i)
#define per4(i,a,b,c) for(ll i=(ll)(a)-1; i>=(ll)(b); i-=(ll)(c))
#define per(...) cut4(__VA_ARGS__,per4,per3,per2,per1)(__VA_ARGS__)
#define per1e(n) for(ll i=(ll)(n); i>=1; --i)
#define per2e(i,n) for(ll i=(ll)(n); i>=1; --i)
#define per3e(i,a,b) for(ll i=(ll)(a); i>=(ll)(b); --i)
#define per4e(i,a,b,c) for(ll i=(ll)(a); i>=(ll)(b); i-=(ll)(c))
#define pere(...) cut4(__VA_ARGS__,per4e,per3e,per2e,per1e)(__VA_ARGS__)
#define rep_subset(i,s) for(ll i=0;i!=-1;i=i==(s)?-1:(i|~(s))+1&(s))
#define per_subset(i,s) for(ll i=(s);i!=-1;i=i==0?-1:i-1&(s))
#define X(p) (p).real()
#define Y(p) (p).imag()

template<class T, class S> bool mkmin(T& a, const initializer_list<S>& b)
{S m = *min_element(all(b)); if(m<a){a=m;return 1;}return 0;}
template<class T, class S> bool mkmax(T& a, const initializer_list<S>& b)
{S m = *max_element(all(b)); if(m>a){a=m;return 1;}return 0;}
template<class T, class S> bool mkmin(T& a, const S& b){if(b<a){a=b;return 1;}return 0;}
template<class T, class S> bool mkmax(T& a, const S& b){if(b>a){a=b;return 1;}return 0;}

#ifdef programstate0
#endif

#ifdef programstate1
// ifstream fin("./special/input.txt");
// ofstream ferr("./special/messages.txt");
// #define cerr ferr
// #define cin fin
#define bug(...) cerr << "#" << __LINE__ << ' ' << #__VA_ARGS__ << "- ", _do(__VA_ARGS__)
template<typename T> void _do(vector<vector<T>> x){cerr << "\n"; for(auto i: x) {for(auto j : i) {cerr << j << ' ';} cerr << "\n";}}
template<typename T> void _do(vector<T> x){for(auto i: x) cerr << i << ' ';cerr << "\n";}
template<typename T> void _do(set<T> x){for(auto i: x) cerr << i << ' ';cerr << "\n";}
template<typename T> void _do(unordered_set<T> x){for(auto i: x) cerr << i << ' ';cerr << "\n";}
template<typename T> void _do(T && x) {cerr << x << endl;}
template<typename T, typename ...S> void _do(T && x, S&&...y) {cerr << x << ", "; _do(y...);}
#else
#define bug(...) 777771449
#endif

const ll MOD = 1e9 + 7;
const ll INF = (1ll << 59);

#ifdef programstate2
const string FILENAME = "infasuratoare";
ifstream fin(FILENAME + ".in");
ofstream fout(FILENAME + ".out");
#define cin fin
#define cout fout
#endif

ll nnt() {ll x; cin >> x; return x;}
string nst() {string x; cin >> x; return x;}
char nct() {char x; cin >> x; return x;}

ld stArea(const cd& a, const cd& b, const cd& c)
{
    return (X(a) * (Y(b) - Y(c)) + X(b) * (Y(c) - Y(a)) + X(c) * (Y(a) - Y(b))) / 2;
}

void convexHull(vec<cd> v, vec<cd>& hull)
{
    rep(i, 1, v.size())
    {
        if(Y(v[i]) < Y(v[0]) || (Y(v[i]) == Y(v[0]) && X(v[i]) < X(v[0]))) swap(v[0], v[i]);
    }

    cd v0 = v[0];
    sort(v.begin()+1, v.end(), [v0](const cd& a, const cd& b)
    {
        ld area = stArea(v0, a, b);

        if(area != 0) return area > 0;

        if(Y(a) == Y(b)) return abs(X(a) - X(v0)) < abs(X(b) - X(v0));
        return Y(a) < Y(b);
    });

    hull.clear();

    for(auto p : v)
    {
        while(hull.size() >= 2)
        {
            cd p0 = hull[hull.size()-2], p1 = hull[hull.size()-1];

            if(stArea(p0, p1, p) <= 0) 
            {
                hull.pop_back();
            }
            else break;
        }

        hull.pb(p);
    }
}

int main()
{
    ll n;
    cin >> n;

    vec<cd> v(n);
    rep(n)
    {
        ld x, y;
        cin >> x >> y;
        v[i] = cd(x, y);
    }

    vec<cd> hull;
    convexHull(v, hull);

    cout << hull.size() << nl;
    cout << fixed << setprecision(6);

    for(auto p : hull)
    {
        cout << X(p) << ' ' << Y(p) << nl;
    }

	return 0;
}