COCI '06 Contest 2 #1 R2

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Points: 3
Time limit: 1.0s
Memory limit: 32M

Problem type

The number S is called the mean of two numbers R_1 and R_2 if S is equal to \frac{R1+R2}{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 -1\,000 and 1\,000.

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

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