Problem 1A
The In between Sum

Description

You are given two numbers, A and B, and you have to find the total of all the numbers between these two numbers. For example if you are given the numbers 9 and 15, you must find the sum 10+11+12+13+14 which is 60.

Input

The input is the pair of integers, A and B (1 <= A <= B <= 30000).

Output

The output will be the sum of all the numbers beteen A and B.

Example 1

Input

9 15

Output

Example 2