Problem:
Score : 400 points

Problem Statement

On a two-dimensional plane, there are N red points and N blue points.
The coordinates of the i-th red point are (a_i, b_i), and the coordinates of the i-th blue point are (c_i, d_i).

A red point and a blue point can form a friendly pair when, the x-coordinate of the red point is smaller than that of the blue point, and the y-coordinate of the red point is also smaller than that of the blue point.

At most how many friendly pairs can you form? Note that a point cannot belong to multiple pairs.

Constraints

All input values are integers.

1 \leq N \leq 100

0 \leq a_i, b_i, c_i, d_i < 2N

a_1, a_2, ..., a_N, c_1, c_2, ..., c_N are all different.

b_1, b_2, ..., b_N, d_1, d_2, ..., d_N are all different.

Input

Input is given from Standard Input in the following format:

N
a_1 b_1
a_2 b_2
:
a_N b_N
c_1 d_1
c_2 d_2
:
c_N d_N

Output

Print the maximum number of friendly pairs.

Sample Input 1

3
2 0
3 1
1 3
4 2
0 4
5 5

Sample Output 1

2

For example, you can pair (2, 0) and (4, 2), then (3, 1) and (5, 5).

Sample Input 2

3
0 0
1 1
5 2
2 3
3 4
4 5

Sample Output 2

2

For example, you can pair (0, 0) and (2, 3), then (1, 1) and (3, 4).

Sample Input 3

2
2 2
3 3
0 0
1 1

Sample Output 3

0

It is possible that no pair can be formed.

Sample Input 4

5
0 0
7 3
2 2
4 8
1 6
8 5
6 9
5 4
9 1
3 7

Sample Output 4

5

Sample Input 5

5
0 0
1 1
5 5
6 6
7 7
2 2
3 3
4 4
8 8
9 9

Sample Output 5

4

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

// OURL: https://atcoder.jp/contests/abc091/tasks/arc092_a
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define REP(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define RREP(i,a,n) for(int i=(a),i##_len=(n);i<i##_len;++i)
#define MAT1D(V,T,a) vector<T> V (a)
#define MAT2D(V,T,a,b) vector<vector<T>> V (a, vector<T>(b))
#define MAT3D(V,T,a,b,c) vector<vector<vector<T>>> V (a, vector<vector<T>>(b, vector<T>(c)))

// http://beet-aizu.hatenablog.com/entry/2018/04/08/145516
template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){ return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...)); }

template<typename T,typename V>
typename enable_if<is_class<T>::value==0>::type
fill_v(T &t,const V &v){t=v;}
template<typename T,typename V>
typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t,const V &v){ for(auto &e:t) fill_v(e,v); }

string to_string(string s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string) s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool>::reference b) { return to_string(bool(b)); }
template <typename A, typename B>
string to_string(pair<A, B> p) { return "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; }
template <typename A>
string to_string(A v) { bool first = true; string res = "{"; for (const auto &x : v) { if (!first) { res += ", "; } first = false; res += to_string(x); } res += "}"; return res; }
template <typename A>
string to_string(vector<vector<A>> v) { string res; for(const auto &x : v) {res+="\n ";res += to_string(x);} return res;}

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) { cerr << " " << to_string(H); debug_out(T...); }

#ifdef LOCAL
#define debug(...) cerr << "[L" << to_string(__LINE__) << ":" <<#__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif


int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n;
  cin >> n;
  auto red = make_v<pair<ll,ll>>(n);
  auto blue = make_v<pair<ll,ll>>(n);
  REP(i,n) {
    ll x,y;
    cin >> x >> y;
    red[i] = make_pair(x,y);
  }
  REP(i,n) {
    ll x,y;
    cin >> x >> y;
    blue[i] = make_pair(x,y);
  }
  // auto inside = make_v<set<int>>(n);
  // auto comp = [](unordered_set<int> x, unordered_set<int> y) {
  //   return x.size() < y.size();
  // };
  // priority_queue<unordered_set<int>, vector<unordered_set<int>>> inside;
  vector<unordered_set<int>> inside;
  REP(j, n) {
    auto &b = blue[j];
    unordered_set<int> s;
    REP(i, n) {
      if (red[i].first < b.first && red[i].second < b.second) {
        s.insert(i);
        // inside[j].insert(i);
      }
    }
    if (s.size()>0) inside.push_back(move(s));
  }
  int ans = 0;
  while(inside.size() > 0) {
    sort(inside.begin(), inside.end(), [](const auto& x, const auto& y) {
          return x.size() > y.size();
        });
    auto it = inside.back(); inside.pop_back();
    if (it.size() > 0) {
      auto r = it.begin();
      for(auto &b : inside) {
        b.erase(*r);
      }
      ans++;
    }
  }
  debug(inside);
  // __uint128_t used = 0;
  // for(auto& ins: inside) {
  //   for(auto& r : ins){
  //     if(!(used & (1<<r))) {
  //       used = used | (1<<r);
  //       ans++;
  //       break;
  //     }
  //   }
  // }

  cout << ans << endl;
  return 0;
}