get a cv::Mat to 2 by 2 maximum value mean? :     0, 1, 0, 0 ,0, 0
    
    0, 0, 2, 0 ,4, 0
    
    0, 1, 0, 5 ,0, 0
    
    0, 0, 1, 0 ,1, 0
    
    0, 0, 0, 0 ,1, 0



I am using opencv.
Assume that cv: mat data is the same as the above array.

I want to get the average of the maximum of 2 by 2 of the array.

As great as

               2, 0 
               0, 5

It will be.
We will divide this value by four to get the average.

How do you get the maximum of 2 by 2?