Rating Goal

AtCoder

IDabc076_a

Time2000ms

Memory256MB

Difficulty—

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: $R$ $G$ [samples]

Samples

Input #1

2002
2017

Output #1

2032

Takahashi's current rating is $2002$.  
If his performance in the contest is $2032$, his rating will be the average of $2002$ and $2032$, which is equal to the desired rating, $2017$.

Input #2

4500
0

Output #2

\-4500

Although the current and desired ratings are between $0$ and $4500$, the performance of a user can be below $0$.

API Response (JSON)

{
  "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 ...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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