#include <bits/stdc++.h>
using namespace std;
#define REP(i,m,n) for(int i = m;i < n;i++)
#define rep(i,n) REP(i,0,n)
#define rrep(i,n) REP(i,1,n+1)
typedef pair<int,int> P;
typedef pair<int, P> PP;
#define fi first
#define se second
const int inf = 1e9;

vector<PP> vs;
multiset<int> s{inf};
int main(){
	int n;
	scanf("%d", &n);
	rep(i,n){
		int x, y;
		scanf("%d%d",&x, &y);
		vs.push_back(PP(x, P(y, 0)));
	}
	rep(i,n){
		int x, y;
		scanf("%d%d", &x, &y);
		vs.push_back(PP(x, P(y, 1)));
	}
	sort(vs.begin(), vs.end());
	
	int ans = 0;
	rep(i,2*n){
		PP pp = vs[i];
		int x = pp.fi, y = pp.se.fi;
		int f = pp.se.se;
		if(f){
			auto it = s.upper_bound(-y);
			if(*it == inf)continue;
			s.erase(it);ans++;
		}else{
			s.insert(-y);
		}
	}
	printf("%d\n", ans);
	return 0;
}
### Prompt

Please formulate a Cpp solution to 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 <bits/stdc++.h>
using namespace std;
#define REP(i,m,n) for(int i = m;i < n;i++)
#define rep(i,n) REP(i,0,n)
#define rrep(i,n) REP(i,1,n+1)
typedef pair<int,int> P;
typedef pair<int, P> PP;
#define fi first
#define se second
const int inf = 1e9;

vector<PP> vs;
multiset<int> s{inf};
int main(){
	int n;
	scanf("%d", &n);
	rep(i,n){
		int x, y;
		scanf("%d%d",&x, &y);
		vs.push_back(PP(x, P(y, 0)));
	}
	rep(i,n){
		int x, y;
		scanf("%d%d", &x, &y);
		vs.push_back(PP(x, P(y, 1)));
	}
	sort(vs.begin(), vs.end());
	
	int ans = 0;
	rep(i,2*n){
		PP pp = vs[i];
		int x = pp.fi, y = pp.se.fi;
		int f = pp.se.se;
		if(f){
			auto it = s.upper_bound(-y);
			if(*it == inf)continue;
			s.erase(it);ans++;
		}else{
			s.insert(-y);
		}
	}
	printf("%d\n", ans);
	return 0;
}
```