Contest: Task: Related: TaskB

Score : $400$ points

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.

- 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 is given from Standard Input in the following format:

$N$ $a_1$ $b_1$ $a_2$ $b_2$ $:$ $a_N$ $b_N$ $c_1$ $d_1$ $c_2$ $d_2$ $:$ $c_N$ $d_N$

Print the maximum number of friendly pairs.

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

2

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

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

2

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

2 2 2 3 3 0 0 1 1

0

It is possible that no pair can be formed.

5 0 0 7 3 2 2 4 8 1 6 8 5 6 9 5 4 9 1 3 7

5

5 0 0 1 1 5 5 6 6 7 7 2 2 3 3 4 4 8 8 9 9

4