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)

#include "bits/stdc++.h"
#define MAXN 200009
#define INF 1000000007
#define mp(x,y) make_pair(x,y)
#define all(v) v.begin(),v.end()
#define pb(x) push_back(x)
#define wr cout<<"----------------"<<endl;
#define ppb() pop_back()
#define tr(ii,c) for(__typeof((c).begin()) ii=(c).begin();ii!=(c).end();ii++)
#define ff first
#define ss second
#define my_little_dodge 46
#define debug(x)  cerr<< #x <<" = "<< x<<endl;
using namespace std;

typedef long long ll;
typedef pair<int,int> PII;
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
int a[MAXN],b[MAXN];
vector<int>v;
int get(int l,int r){
	int x=lower_bound(all(v),l)-v.begin();
	int y=upper_bound(all(v),r)-v.begin();
	return y-x;
}
int main(){
    //~ freopen("file.in", "r", stdin);
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
		scanf("%d",a+i);
	for(int i=0;i<n;i++)
		scanf("%d",b+i);
	int res=0;	
	for(int h=0;h<29;h++){
		v.clear();int mod=(1<<(h+1));
		int T=mod/2;
		for(int i=0;i<n;i++)
			v.pb(b[i]%mod);
		sort(all(v));	
		ll ans=0;
		for(int i=0;i<n;i++){
			int res=(a[i]%mod);
			//T and 2*T
			if(res<T)
				ans+=get(T-res,2*T-1-res);	
			else if(res<2*T){
				ans+=get(0,2*T-1-res);
				ans+=get(3*T-res,4*T-1-res);
			}
			else
				ans+=get(3*T-res,4*T-1-res);
			//3*T and 4*T
		}
		if(ans&1)
			res+=T;
	}printf("%d\n",res);
	return 0;
}