Sum of Consecutive Odd Numbers I

Source: beecrowd

Version: Phuoc Hung OJ Extended

Problem Statement

Given x and y, sum all odd integers strictly between them, excluding both endpoints regardless of input order.

Input

Two integers x,y in [-10000,10000] (PHOJ Extended bound).

Output

One integer: the sum of odd integers strictly between.

Subtasks

• Subtask 1 (20%): $|x|,|y|\le10$.
• Subtask 2 (30%): $|x|,|y|\le1000$.
• Subtask 3 (50%): $|x|,|y|\le10000$.

Examples

Example 1

Input

6
-5

Output

5

Explanation

Odd values -3,-1,1,3,5 sum to 5.

Example 2

Input

7 8

Output

0

Explanation

Consecutive endpoints leave an empty interval.