##### Woburn Challenge 2018-19 Round 4 - Junior Division

Billy, the king of video games, began his career off the back of a
particular arcade game: *Donkey Kong*. Though he's masterfully played
many other games since, there's nothing quite like popping in a few
quarters and returning to the arcade classic.

Beginning a game of *Donkey Kong* requires the player to first insert at
least dollars in change. Billy had previously
already inserted quarters into his personal
*Donkey Kong* arcade cabinet. He's now looking to insert zero or more
additional quarters so that he can start playing.

What's the minimum number of additional quarters which Billy must insert such that the total amount of inserted change will come out to at least dollars?

#### Input Specification

The first line of input consists of a single integer, .

The next line consists of a single integer, .

#### Output Specification

Output a single integer, the number of additional quarters which Billy must insert.

#### Sample Input 1

```
2
3
```

#### Sample Output 1

`5`

#### Sample Input 2

```
1
20
```

#### Sample Output 2

`0`

#### Sample Explanation

In the first case, Billy has already inserted ( quarters), and must insert an additional ( quarters) to bring his total up to at least .

In the second case, Billy has already inserted at least worth of quarters, so no more are required.

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