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: Accepted)

#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVS vector<vector<string>>
#define VVC vector<vector<char>>
typedef long long ll;
const int  INF = 2147483647;
const ll INFL = 1LL << 50;
const ll mod = 1000000007;




int main() {
	int n;
	cin >> n;
	vector<pair<int, int>> a, b;
	REP(i, n) {
		int c, d;
		cin >> c >> d;
		a.push_back(make_pair(c, d));
	}
	REP(i, n) {
		int c, d;
		cin >> c >> d;
		b.push_back(make_pair(c, d));
	}

	sort(ALL(a));
	sort(ALL(b));
	int res = 0;
	VI v(n + 10, 0);
	REP(i, n) {
		int c = 0, d = -1;
		REP(j, n) {
			if (v[j]==0 && a[j].first < b[i].first && a[j].second < b[i].second) {
				if (c <= a[j].second) {
					c = a[j].second;
					d = j;
				}
			}
		}
		if (d>=0) {
			v[d] = 1;
			res++;
		}
	}
	cout << res << endl;
	
	return 0;
}