The number $S$ is called the mean of two numbers $R_1$ and $R_2$ if $S$ is equal to $\frac{R_1+R_2}{2}$. Mirko's birthday present for Slavko was two integers $R_1$ and $R_2$. Slavko promptly calculated their mean which also happened to be an integer but then lost $R_2$! Help Slavko restore $R_2$.

Input Specification

The first and only line of input contains two integers $R_1$ and $S$, both between $-1000$ and $1000$.

Output Specification

Output $R_2$ on a single line.

Sample Input 1

11 15

Sample Output 1

19

Sample Input 2

4 3

Sample Output 2

2