How to number a list of lines in org mode

I never had to number a list of lines so many times until my most recent study on TCP sequence numbers.

Paste a bunch of lines, and use the string-rectangle command to insert "1." at the beginning:

1. hello
2. world
3. .

Finally, move the cursor to any of thes lines and press C-c:

1. hello
2. world
3. .