Fix the indentation

In the given snippet, there's a bug: there's no indentation.

Your goal is to fix it (by just adding 4 spaces at the right place).

The code should display:

Gonna knock three times:
*knock*
*knock*
*knock*
- Who's there?

What's indentation?

As you may have guessed by reading the actual code, after the for line asking Python to repeat three times, Python can't guess what should be repeated: should Python only repeat print("*knock*") or should Python print the two following print?

To indicate this in Python we do use 4 spaces in front of the lines, like this:

for i in range(5):
    print("Hello")

which will display:

Hello
Hello
Hello
Hello
Hello