**25 人解决**，35 已尝试。

**50 份提交通过**，共有 146 份提交。

**8.1** EMB 奖励。

**单测试点时限: **3.0 秒

**内存限制: **256 MB

A number is perfect if it is equal to the sum of its divisors, the ones that are smaller than it. For example, number is perfect because .

Motivated by this definition, we introduce the metric of imperfection of number , denoted with , as the absolute difference between and the sum of its divisors less than . It follows that perfect numbers’ imperfection score is , and the rest of natural numbers have a higher imperfection score. For example:

- ,
- ,
- .

Write a programme that, for positive integers and , calculates the sum of imperfections of all numbers between and : .

The first line of input contains the positive integers and ().

The first and only line of output must contain the required sum.

Input

24 24

Output

12

Input

1 9

Output

21

Clarification of the first test case: .