Given a character matrix, your task is to identify the positions of all squares with a length of at least 3 and output the row and column numbers of the bottom-right corner of these squares. The squares are composed of the same character, and each side has a length of at least 3.

If the matrix is

J H E U I L V R D
G A S N G N P M K
Z H Z F Z L R B C
E P R P T J B N A
S U A L X U A P V
N H R T P B L Y M
U O X D E J Q X E
W O M E W Q H J H
W W D F T N I E V
C I Z U Y L M Y W
Y T W Q K T G O N
X X X P G H X C L
X X X K A X A K T
X X X Y I H I B T
R G G S I W P V S

Please provide the row and column of the bottom-right vertex of the square in the character matrix with a side length of at least 3 (the answer is unique). Notice: All coordinates start from 0.  

Your answer should be in the format <<<[row, column]>>>.