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 JavaScript (node.js v5.12) (judge verdict: Wrong Answer)

"use strict";

function main(input) {
  var inputs = input.split("\n");

  var N = parseInt(inputs[0], 10)
  var a = inputs.slice(1, N + 1).map((v, i) =>
    v.split(" ").map((v, i) => parseInt(v, 10))
  );
  var c = inputs.slice(N + 1, 2 * N + 1).map((v, i) =>
    v.split(" ").map((v, i) => parseInt(v, 10))
  );
  a.sort((a, b) => b[1] - a[1]);
  c.sort((a, b) => a[0] - b[0]);

  console.log("a");
  console.log(a.reduce((acc, v) => acc + "\n" + v));
  console.log("c");
  console.log(c.reduce((acc, v) => acc + "\n" + v));


  var result = 0;

  for (let ci = 0; ci < c.length; ci++) {
    for (let ai = 0; ai < a.length; ai++) {
      if (a[ai][0] < c[ci][0] && a[ai][1] < c[ci][1]) {
        a[ai][0] = a[ai][1] = 100 * N;
        result++;
        break;
      }
    }
  }

  console.log(result);
}

main(require("fs").readFileSync("/dev/stdin", "utf8"));