Sum of even numbers from A to B

C++ Easy math

Task «Sum of even numbers from A to B»

The input consists of two integers A and B. It is necessary to find the sum of all even numbers in the range from A to B inclusive. It is guaranteed that A ≤ B. Solve the problem without using loops, using the arithmetic progression formula.

Input Format

Two integers A and B, separated by a space.

Output Format

One integer — the sum of even numbers from A to B.

Examples

Example 1

INPUT

1 10

OUTPUT

30

Example 2

INPUT

2 6

OUTPUT

12

main.cpp