# R2

The number $S$ is called the mean of two numbers $R_1$ and $R_2$ if $S$ is equal to $(R_1+R_2)/2$. 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

The first and only line of input contains two integers $R_1$ and $S$, both between $-1\, 000$ and $1\, 000$.

## Output

Output $R_2$ on a single line.

Sample Input 1 | Sample Output 1 |
---|---|

11 15 |
19 |

Sample Input 2 | Sample Output 2 |
---|---|

4 3 |
2 |