AtCoder Beginner Contest 091 C - 2D Plane 2N Points

C - 2D Plane 2N Points

Time limit : 2sec / Memory limit : 256MBScore : 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 (ai,bi), and the coordinates of the i-th blue point are (ci,di).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 c
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an you form? Note that a point cannot belong to multiple pairs.

Constraints

All input values are integers.
1≤N≤1000≤ai,bi,ci,di<2N
a1,a2,…,aN,c1,c2,…,cN are all different.
b1,b2,…,bN,d1,d2,…,dN are all different.

Input

Input is given from Standard Input in the following format:N
a1 b1
a2 b2:
aN bN
c1 d1
c2 d2:
cN dN

Output

Print the maximum number of friendly pairs.

Sample Input 1

Copy

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

Sample Output 1

Copy

2

For example, you can pair (2,0) and (4,2), then (3,1) and (5,5).

Sample Input 2

Copy

3
0 01 1
5 22 3
3 4
4 5

Sample Output 2

Copy

2

For example, you can pair (0,0) and (2,3), then (1,1) and (3,4).

Sample Input 3

Copy

22 23 3
0 01 1

Sample Output 3

Copy

0

It is possible that no pair can be formed.

Sample Input 4

Copy

50 07 3
2 24 8
1 6
8 56 9
5 4
9 1
3 7

Sample Output 4

Copy

5

Sample Input 5

Copy

50 01 1
5 56 6
7 7
2 23 3
4 4
8 8
9 9

Sample Output 5

Copy

4

这题说实在我也不太明白，后来把两组分别以x，y做升序和降序居然ac了，不可思议，后来学弟和我说这其实是利用了找两个点最接近的原理，玄学+谜