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.
r = float(input())
g = float(input())


print(g*2 - r)
r = int(input())
g = int(input())


print(g*2 - r)