#You need to debug and modify the program so that it is able to do random walking

import random

N $=10$

FILLER $=\text{'}.\text{'}$

#create a list to represent a row

#The row at first is filled with FILLER $\text{'}.\text{'}$

line $=[]$

for i in range$($N$)$:

line.append$($FILLER$)$

#create a matrix

#The matrix is the maze to walk

a$=[]$

for i in range$($N$)$:

line $=$ line$[$:$]$

a$.$append$($line$)$

#always starts at the left top corner of the matrix

#fill the matrix cell at the left top corner $\text{'}$A$\text{'}$

x $=0$

y $=0$

letter $=\text{'}$A$\text{'}$

a$[$x$][$y$]=$ letter

#a sequence of random walk steps

#The below loop will settle the next letter

letter $=$ chr$($ord$($letter$)+1)$

#The following loop broken due to

#running out of letters

while $($letter $<=\text{'}$Z$\text{'})$:

#find $($x$,$y$)$ for the current letter

#check the interative book chapter $5\mathrm{.}4$ random module for methods to use

#update the letter to present