Suppose u have a square matrix, where every cell is filled with 0 or 1 . U need to find the maximum subsquare such that all four borders are filled with all 1s.

Ex:- 

1 0 0 1 1 0 
1 0 1 1 1 0 
0 0 1 0 1 1 
0 1 1 1 1 0 
1 0 0 1 1 1 


Here the maximum square (3X3) possible is from the TOP LEFT (2 3) TO 
BOTTOM RIGHT (4 5) .