Problem Statement

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.