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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

fun main(args: Array<String>) {

    val n = readInt()
    val reds = (1..n).map {
        val (a, b) = readIntList()
        Pos(a, b)
    }.sorted().toMutableList()
    val blues = (1..n).map {
        val (c, d) = readIntList()
        Pos(c, d)
    }.sorted().toMutableList()
    val num = blues.mapNotNull { blue ->
        val red = reds.find { it.x < blue.x && it.y < blue.y }
        if (red != null) reds.remove(red)
        red
    }.count()
    /*val count = reds.mapNotNull { red ->
        val blue = blues.find { it.x > red.x && it.y > red.y }
        if (blue != null) blues.remove(blue)
        blue
    }.count()*/
    println(num)
}

data class Pos(val x: Int, val y: Int) : Comparable<Pos> {
    override fun compareTo(other: Pos): Int {
        val minThis = Math.min(x, y)
        val minOther = Math.min(other.x, other.y)
        val sumThis = x + y
        val sumOther = other.x + other.y
        return if (minThis > minOther) 1 else if (minThis < minOther) -1 else if (sumThis > sumOther) 1 else if (sumThis < sumOther) -1 else 0
    }
}

fun printYesOrNo(flag: Boolean) {
    println(if (flag) "Yes" else "No")
}

fun readIntList(): List<Int> = readLine()!!.split(' ').map { it.toInt() }

fun readInt(): Int = readLine()!!.toInt()

fun err(print: Any) {
    System.err.println(print)
}