Using *if* statements is the same in the nested loops as in the single `while` or `for` loop.

matrix = [[1, -4, 4, 29],
     [3, 4, -200, -1],
     [10, -5, 0, 8]]

# Changing negative numbers to 'N'
i = 0
#  Setting outer while loop to work with the number of rows 
while i < len(matrix):
  j = 0
  #  Setting inner while loop to work with the number of elements in the row
  while j < len(matrix[i]):
    if matrix[i][j] > 0:
      print(matrix[i][j], end = ' ')
    else:
      print('N', end = ' ')
    j +=1
  i += 1
  print('')

We have just seen an example of using *if/else* inside the nested loop while working with the matrix.
In your task, you will work with 2 strings.
Use hints if needed!

We start learning Python loops with the for loop. A for loop is used for iterating over a sequence. Let's go!

With the while loop, we can execute a set of statements as long as a condition is true. We are going to work with this loop and handle different problems!

A nested loop is a loop inside a loop. Sound difficult? Don't worry! We will handle this loop!