# Mean arithmetic

Execution time limit is 1 second

Runtime memory usage limit is 256 megabytes

Petrik has two numbers $a$ and $b$ ($a≤b$). He found the arithmetic mean of these numbers (let it be the number $c$), which turned out to be an integer. That is, $c=2a+b $.

You are given the number $a$ (i.e. the smaller of the two numbers), as well as the number $c$. Find $b$.

## Input

The first line contains an integer $a$ ($1≤a≤100$).

The second line contains an integer $c$ ($a≤c≤100$).

## Output

Output one integer — $b$.

## Examples

Input #1

Answer #1

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