Sum of Even Numbers in a Range

Given two integers start and end, compute the sum of all even numbers in the inclusive range \( [start, end] \). The formula used to calculate the sum when there are \( n \) even numbers ranging from \( a \) to \( b \) is:

\( \text{sum} = \frac{n (a + b)}{2} \)

If the range is invalid or contains no even numbers, the result should be 0.

inputFormat

A single line containing two space-separated integers, representing the start and end of the range.

outputFormat

An integer representing the sum of all even numbers within the given range.## sample

2 10

30