## COCI '06 Contest 2 #1 R2

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

Problem type

The number is called the mean of two numbers and if is equal to . Mirko's birthday present for Slavko was two integers and . Slavko promptly calculated their mean which also happened to be an integer but then lost ! Help Slavko restore .

#### Input Specification

The first and only line of input contains two integers and , both between and .

#### Output Specification

Output on a single line.

#### Sample Input 1

11 15

#### Sample Output 1

19

#### Sample Input 2

4 3

#### Sample Output 2

2