Input
====

A list of lists of letters like:

 ["B", "C", "C", "C", "C", "B", "B", "C", "A", "A"],
 ["B", "A", "C", "B", "B", "A", "B", "B", "A", "A"],
 ["B", "C", "B", "C", "A", "A", "A", "B", "C", "B"],
 ["B", "B", "B", "A", "C", "B", "A", "C", "B", "A"],
 ["A", "A", "A", "C", "A", "C", "C", "B", "A", "C"],
 ["A", "B", "B", "A", "A", "C", "B", "C", "C", "C"],
 ["C", "B", "A", "A", "C", "B", "B", "C", "A", "A"]

Rules
===

* To make a valid rectangle you need all rectangle corners of the same color.
* Example, look the *sample board with* **X** bellow. You can see 'X' on (1,0) also on (4,0) also on ( 1,3) and on (4,3) then you have the rectange [1,0,4,3] that means from (1,0) to (4,3):

*Sample board with* **X**:

 ["B", "X", "C", "C", "X", "B", "B", "C", "A", "A"],
 ["B", "A", "C", "B", "B", "A", "B", "B", "A", "A"],
 ["B", "C", "B", "C", "A", "A", "A", "B", "C", "B"],
 ["B", "X", "B", "A", "X", "B", "A", "C", "B", "A"],
 ["A", "A", "A", "C", "A", "C", "C", "B", "A", "C"],
 ["A", "B", "B", "A", "A", "C", "B", "C", "C", "C"],
 ["C", "B", "A", "A", "C", "B", "B", "C", "A", "A"]

* The goal is to found the valid rectangle with the largest **area**

Output
====

The output should be the left-up and right-down positions of the largest area rectangle corners. For the first sample "board" the big square is the yellow one:

[![enter image description here][1]][1]

And the answer should be:

> [1, 1, 8, 4]

This question is posted on Stack Overflow with title: [How to find the largest rectangle in a 2D array formed by four identical corners?][2] and with this rude JS solution (I can say "rude" because is my code ;) :

Ok, is my first post, be tolerant with me please. I will change all you say to improve the quiz.

 [1]: https://i.sstatic.net/ZIkkF.png
 [2]: https://stackoverflow.com/questions/49708412/how-to-find-the-largest-rectangle-in-a-2d-array-formed-by-four-identical-corners