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 <algorithm>
//#include <cstdio>
//#include <functional>
#include <iostream>
//#include <cfloat>
//#include <climits>
//#include <cstdlib>
//#include <cstring>
//#include <cmath>
//#include <map>
//#include <queue>
//#include <set>
//#include <sstream>
//#include <stack>
//#include <string>
//#include <time.h>
//#include <vector>
//#include <random>
//#include <unordered_set>
//#include <complex>
#define WAIT system ("pause")
#define rt0 return 0
using namespace std;
int main()
{
	int N, A[100],B[100],C[100],D[100];
	int big[100],small[100];
	
	cin>>N;
	for(int i=0;i<N;i++){
		cin>>A[i]>>B[i];
		big[i]=0;
	} 
	for(int i=0;i<N;i++){
		cin>>C[i]>>D[i];
		small[i]=0;
		for(int j=0;j<N;j++){
			if(A[j]<C[i] and B[j]<D[i]){
				small[i]++;
				big[j]++;
			}
		}
	} 
	
	int ans=0;
	while(1){
		int k=-1;
		int count=101;
		for(int i=0;i<N;i++){
			if(small[i]<=0) continue;
			if(small[i]<count){
				k=i;
				count=small[i];
			}
		}
		if(count>100) break;
		
		small[k]=0;
		count=0;
		int x=-1;
		int count1=101;
		for(int j=0;j<N;j++){
			if(big[j]<=0) continue;
			if(A[j]<C[k] and B[j]<D[k]){
				big[j]--;
				if(big[j]<count1) {
					count1=big[j];
					x=j;
				}
				count++;
			}
		}
		if(count>0) ans++;
		if(x>=0) {
			big[x]=0;
			for(int i=0;i<N;i++){
				if(A[x]<C[i] and B[x]<D[i]) small[i]--;
			}
		}
	}
	cout<<ans;
	
    rt0;
}