Arithmetic Mean

Cossack Vus has two integers $a$ and $b$ ($a\le b$). He found the arithmetic mean of these numbers (let it be the number $c$). That is, $c=\frac{a+b}{2}$.

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 one integer $a$ ($1\le a\le 100$).

The second line contains one integer $c$ ($a\le c\le 100$).

Output

Output one integer — $b$.

Examples