Problems
Arithmetic mean
Arithmetic mean
Petya has two numbers a and b (a ≤ b). He found the arithmetic mean of these numbers (let it be the number c), that also turned out to be an integer. That is, c = (a + b) / 2.
You are given the number a (that is, the smallest of two numbers), and you are also given the number c. Find b.
Input data
The first line contains one integer a (1 ≤ a ≤ 100).
The second line contains a single integer c (a ≤ c ≤ 100).
Output
Print one integer b.
Input example #1
3 7
Output example #1
11