Partial Interval Sum

Problem Background

Special for beginners, ^_^

Problem Description

Given a sequence of $n$ integers, compute the sum of the numbers in the range $[a, b]$.

$$\nsum(a, b) =\n\begin{cases}\nnum[a], &a=b\\\\\nnum[a]+sum(a+1, b), &a < b\n\end{cases}\n$$

Input Format

The first line contains a positive integer $n\;(1\lt n \le 10^5)$.

The second line contains $n$ positive integers, each less than $10^6$.

The third line contains two integers $a, b$.

Output Format

Output the sum of the integers in the range $[a, b]$.

Sample Input

5
1 2 3 4 5
2 4

Sample Output

9

Constraints

1s, 1024KiB for each test case.