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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>
struct ln
{
        int x;
        int y;
        int z;
}a[200],b[200];
int cmp(const void*a,const void *b)
{
        struct ln *c=(struct ln*)a;
        struct ln *d=(struct ln*)b;
        if(c->x!=d->y)
                return d->x-c->x;
        else
                return d->y-c->y;
}
int main()
{
    int n,i,j,x1,y1,flag,w,s=0;
    scanf("%d",&n);
     for(i=0;i<n;i++)
        scanf("%d%d",&a[i].x,&a[i].y),a[i].z=0;
     for(i=0;i<n;i++)
        scanf("%d%d",&b[i].x,&b[i].y),b[i].z=0;
      qsort(a,n,sizeof(a[0]),&cmp);
      qsort(b,n,sizeof(b[0]),&cmp);
      for(i=0;i<n;i++)
      {
          x1=10000,y1=10000,flag=0;
          for(j=0;j<n;j++)
          {
              if(a[i].x<b[j].x&&a[i].y<b[j].y&&b[i].x<x1&&b[i].y<y1)
              {
                  x1=b[i].x;
                  y1=b[i].y;
                  w=j;
                  flag=1;
              }
          }
          if(flag==1)
          {
              s++;
              b[w].x=-1;
              b[w].y=-1;
          }
      }
      printf("%d\n",s);
      return 0;
}