p03563 AtCoder Beginner Contest 076 - Rating Goal
Takahashi is a user of a site that hosts programming contests.
When a user competes in a contest, the rating of the user (not necessarily an integer) changes according to the performance of the user, as follows:

* Let the current rating of the user be a.
* Suppose that the performance of the user in the contest is b.
* Then, the new rating of the user will be the avarage of a and b.



For example, if a user with rating 1 competes in a contest and gives performance 1000, his/her new rating will be 500.5, the average of 1 and 1000.

Takahashi's current rating is R, and he wants his rating to be exactly G after the next contest.
Find the performance required to achieve it.

Constraints

* 0 \leq R, G \leq 4500
* All input values are integers.

Input

Input is given from Standard Input in the following format:


R
G


Output

Print the performance required to achieve the objective.

Examples

Input

2002
2017


Output

2032


Input

4500
0


Output

-4500
```python
r=float(input())
g=float(input())
print(int(2*g-r))

```