Mean arithmetic
Execution time limit is 1 second
Runtime memory usage limit is 256 megabytes
Petrik has two numbers and (). He found the arithmetic mean of these numbers (let it be the number ), which turned out to be an integer. That is, .
You are given the number (i.e. the smaller of the two numbers), as well as the number . Find .
Input
The first line contains an integer ().
The second line contains an integer ().
Output
Output one integer — .
Examples
Input #1
Answer #1
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