#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int main(void) {
  int N; cin >> N;
  vector<pair<int, int>> R, B;
  for (int i = 0; i < N; i++) {
    int xi, yi; cin >> xi >> yi;
    R.push_back(make_pair(yi, xi));
  }
  for (int i = 0; i < N; i++) {
    int xi, yi; cin >> xi >> yi;
    B.push_back(make_pair(xi, yi));
  }
  sort(R.begin(), R.end());
  reverse(R.begin(), R.end());
  sort(B.begin(), B.end());

  int count = 0;
  vector<bool> used(N, false);
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++) {
      if (!used[j] && R[i].first < B[j].second && R[i].second < B[j].first) {
        used[j] = true;
        count++;
        break;
      }
    }
  }

  cout << count << endl;
}

### Prompt

Create a solution in cpp for the following problem:

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.

Examples

Input

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


Output

2


Input

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


Output

2


Input

2
2 2
3 3
0 0
1 1


Output

0


Input

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


Output

5


Input

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


Output

4

### Response

```cpp
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

int main(void) {
  int N; cin >> N;
  vector<pair<int, int>> R, B;
  for (int i = 0; i < N; i++) {
    int xi, yi; cin >> xi >> yi;
    R.push_back(make_pair(yi, xi));
  }
  for (int i = 0; i < N; i++) {
    int xi, yi; cin >> xi >> yi;
    B.push_back(make_pair(xi, yi));
  }
  sort(R.begin(), R.end());
  reverse(R.begin(), R.end());
  sort(B.begin(), B.end());

  int count = 0;
  vector<bool> used(N, false);
  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++) {
      if (!used[j] && R[i].first < B[j].second && R[i].second < B[j].first) {
        used[j] = true;
        count++;
        break;
      }
    }
  }

  cout << count << endl;
}

```