I am at the moment of understanding how lists and while loops work in Python. Unfortunately, I am a bit confused with my code.

```
main_list = []
list_1 = [1, 2]
list_2 = [3, 4]

i = 0
n = 2

while i != n:

    number = int(input("Insert a number: "))

    list_1.append(number)
    main_list.append(list_1)
    main_list.append(list_2)

    i += 1

print(main_list)

```

Why am I getting an output of this,

```
>> Insert a number: 2
>> Insert a number: 3
>> [[1, 2, 2, 3], [3, 4], [1, 2, 2, 3], [3, 4]]

```

instead of this?

```
>> Insert a number: 2
>> Insert a number: 3
>> [[1, 2, 2], [3, 4], [1, 2, 2, 3], [3, 4]]

```

I would appreciate if anyone can explain it to me, thank you.