Sum of Consecutive Odd Numbers III

Source: beecrowd

Version: Phuoc Hung OJ Extended

Problem Statement

Given integers X and Y, sum exactly Y consecutive odd integers starting from the smallest odd integer not smaller than X.

Input

One line contains X Y; there is no leading case count.

Output

Print the required integer sum.

Subtasks

• Subtask 1 (20%): -20 ≤ X ≤ 20, Y ≤ 10.

• Subtask 2 (30%): -1000 ≤ X ≤ 1000, Y ≤ 100.

• Subtask 3 (50%): -100000 ≤ X ≤ 100000, Y ≤ 100000.

Examples

Example 1

Input:

4 3

Output:

21

Explanation: The sequence is 5, 7, 9, summing to 21.

Example 2

Input:

-3 3

Output:

-3

Explanation: The sequence is -3, -1, 1, summing to -3.