No testdata at current.

Background

Special for beginners, ^_^

Description

Given two integers n and m, print the sum of $n+(n+1)+(n+2)+...+(m-2)+(m-1)+m$ .

Format

Input

Two integers n and m.

Output

One integer, the sum of $n+(n+1)+(n+2)+...+(m-2)+(m-1)+m$ .

Samples

1 10

55

Limitation

1s, 1024KiB for each test case.

$-10^{99999} \leq n \leq m \leq 10^{99999}$