{"problem":{"name":"Rating Goal","description":{"content":"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 ","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"abc076_a"},"statements":[{"statement_type":"Markdown","content":"Takahashi is a user of a site that hosts programming contests.  \nWhen 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:\n\n*   Let the current rating of the user be $a$.\n*   Suppose that the performance of the user in the contest is $b$.\n*   Then, the new rating of the user will be the avarage of $a$ and $b$.\n\nFor 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 $1000$.\nTakahashi's current rating is $R$, and he wants his rating to be exactly $G$ after the next contest.  \nFind the performance required to achieve it.\n\n## Constraints\n\n*   $0 \\leq R, G \\leq 4500$\n*   All input values are integers.\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$R$\n$G$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"abc076_a","tags":[],"sample_group":[["2002\n2017","2032\n\nTakahashi's current rating is $2002$.  \nIf his performance in the contest is $2032$, his rating will be the average of $2002$ and $2032$, which is equal to the desired rating, $2017$."],["4500\n0","\\-4500\n\nAlthough the current and desired ratings are between $0$ and $4500$, the performance of a user can be below $0$."]],"created_at":"2026-03-03 11:01:14"}}