Age Problem

Problem Background

Special for beginners, ^_^

Problem Description

Xiaoming is $a$ years old this year, and his father is $b$ years old. Xiaoming wants to know after how many years his father's age will be twice his own. Can you help him?

Input Format

The input gives two int values $a$ and $b$: Xiaoming's age and his father's age respectively.

Output Format

Output one integer $n$: the number of years after which the father's age will be twice Xiaoming's.

Sample Input

3 30

Sample Output

24

Constraints

1s, 1024KiB for each test case.

Hint

• "After n years the father's age is exactly twice Xiaoming's" — turn this sentence into an equation and solve for n.
• One line of arithmetic gives the answer; no loop or branch is needed.
• Verify with the sample: 3 30 → 24.