Minimum Days to Reach Target

Little B loves programming. He has already solved \( x \) problems. In the upcoming days, he can solve either \(1\) or \(2\) problems per day. Determine the minimum number of days required for him to have solved at least \( y \) problems. Mathematically, if \(x < y\), the answer is given by \(\lceil \frac{y-x}{2} \rceil\); otherwise, the answer is 0.

inputFormat

The input consists of two space-separated integers \(x\) and \(y\), where \(x\) is the number of problems already solved and \(y\) is the target number of problems.

outputFormat

Output a single integer representing the minimum number of days required to reach at least \( y \) problems.

sample

10 10

0