Arithmetic mean#11301
Petya has two numbers and (a \le b). He found the arithmetic mean of these numbers (let it be the number ), that also turned out to be an integer. That is, c = (a + b) / 2.
You are given the number (that is, the smallest of two numbers), and you are also given the number . Find .
The first line contains one integer (1 \le a \le 100).
The second line contains a single integer (a \le c \le 100).
Print one integer .
Example 1