2D Subarray Sum

题面

计算二维数组子矩形 input[S_ROW..E_ROW][S_COL..E_COL] 的元素和（行列索引均为 0-based 含端点）。

Implementation Requirements

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

Examples

[[1,2,3],[4,5,1]], (0..1, 1..2) → 11
[[5,10],[5,2]], (0..0, 1..1) → 10

Constraints

• 1 ≤ N, M ≤ 10,000
• 1 ≤ input[i] ≤ 10
• 0 ≤ S_ROW ≤ E_ROW ≤ N-1；0 ≤ S_COL ≤ E_COL ≤ M-1
• Performance: N = 10,000, M = 10,000