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

inputFormat

input values are integers.

Input

Input is given from Standard Input in the following format:

R G

outputFormat

Output

Print the performance required to achieve the objective.

Examples

Input

2002 2017

Output

2032

Input

4500 0

Output

-4500

样例

4500
0

-4500