There are clowns, pairs of shoes, and shoe colours. Each clown has a favourite shoe colour . Each clown also has a shoe size , and can only wear shoes with size . Assuming every clown must be given a pair of shoes that they can wear, how many can get their favourite colour?

#### Input Specification

The first line will contain two integers and .

The next lines will contain integers and , the colour and size of the shoe respectively.

The next lines will contain integers and , the favourite colour and shoe size of the clown respectively.

It is guaranteed that it is possible to distribute the shoes among the clowns such that each clown is given a pair of shoes that they can wear.

#### Output Specification

On one line you are to output one integer, the number of clowns who can wear shoes of their favourite color in a valid distribution.

#### Subtasks

##### Subtask 1 (5%)

##### Subtask 2 (20%)

##### Subtask 3 (75%)

No further constraints.

#### Sample Input

```
3 9
3 3
3 9
2 4
2 3
1 5
3 4
```

#### Sample Output

`0`

## Comments