Polygon

Seunghyun drew the figure below on a sheet of paper.

He noticed that for the quadrilateral at the bottom, a single straight line cuts all four sides.

That made him wonder how many sides such a polygon can have.

Write a program that adds up every $n$ for which an $n$-gon exists whose sides can all be cut by one straight line. There are infinitely many such $n$, so count only the ones with $n$ between $a$ and $b$, inclusive. A polygon has at least three sides, so $n$ is at least 3.

The first line contains two natural numbers $a$ and $b$, separated by one space. ($1 \le a \le b \le 10^9$)

Print the sum of every $n$ that satisfies the condition on the first line.