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.

Examples