Given a matrix and an integer k, return the maximum sum of any rectangular submatrix such that the sum is no larger than k. The input is JSON {matrix, k}.
Input: JSON {matrix, k}.
Output: Integer — the maximum submatrix sum not exceeding k.
Input: {"matrix":[[1,0,1],[0,-2,3]],"k":2}
Output: 2
Explanation: The rectangle summing to 2 is the largest not exceeding k.Input: {"matrix":[[2,2,-1]],"k":3}
Output: 3
Explanation: 2 + 2 - 1 = 3.Input: {"matrix":[[5]],"k":5}
Output: 5
Explanation: Single cell.1<=rows,cols<=100