Background

JerryC has recently become obsessed with Asphalt Racing.

Problem Description

As everyone knows, JerryC is a crazy Female. He recently bought a sports car (but he does not have a driver’s license), so he can only practice driving in a remote place.

Of course, JerryC is not going to drive normally. She first decides to drive $(B-A+1)$ segments of road. In the $i$-th segment, the speed starts accelerating from $1$. Each second, it increases by $1$ unit of speed. When the speed reaches $(i+A-1)$, JerryC will reduce the speed back to $1$, and then start the next segment.

For the $j$-th second of the $i$-th segment, the pleasure value JerryC gets is $\left\lfloor \frac{i+A-1}{j} \right\rfloor \times (-1)^j$. (Anyway, JerryC just does not like odd numbers.)

Now please compute JerryC’s final total pleasure value.

P.s.:

If you did not understand the above, then the simplified version is:

Given $A, B$, compute the value of the following expression.

$$\sum_{i=A}^B \sum_{j=1}^{i}\left\lfloor \frac{i}{j} \right\rfloor \times (-1)^j$$

Input Format

One line with two positive integers $A, B$.

Output Format

One line with one integer, representing the final pleasure value.

1 1

-1

2 2

-1

3 3

-3

Hint

For $50\%$ of the testdata, $1 \leqslant A \leqslant B \leqslant 5\times10^3$.
For $70\%$ of the testdata, $1 \leqslant A \leqslant B \leqslant 5\times10^4$.
For $100\%$ of the testdata, $1 \leqslant A \leqslant B \leqslant 2\times10^7$.

Translated by ChatGPT 5