Why does the code block if I enter number greater than 3 or less than -4 in line 9?

Question

https://code.sololearn.com/c9i8gl1xt5n5/?ref=app

Answer 1

Each position in the list has two indexes to access it as shown below:
[0, 1, 2, 3] #List contents
0 1 2 3 #Positive indexes
-4 -3 -2-1 #Negative indexes

Answer 2

thats how list manipulation work. Those are the maximum selectable / index values