Given a rows x cols binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.

  Example 1:

Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]] Output: 6 Explanation: The maximal rectangle is shown in the above picture.

Example 2:

Input: matrix = [["0"]] Output: 0

Example 3:

Input: matrix = [["1"]] Output: 1

  Constraints:

rows == matrix.length
cols == matrix[i].length
1 <= row, cols <= 200
matrix[i][j] is '0' or '1'.