Subarray Sum

题面

计算整型数组 input[S..E] 的区间和（S、E 为包含端点，0-based）。

Implementation Requirements

• Use only native features (external libraries are not permitted)
• The solve function signature must remain unchanged
• 结果写入 output

Examples

[1,2,1,3,4], S=1, E=3 → 6
[1,2,3,4], S=0, E=3 → 10

Constraints

• 1 ≤ N ≤ 100,000,000
• 1 ≤ input[i] ≤ 10
• 0 ≤ S ≤ E ≤ N-1
• Performance: N = 100,000,000