Now, you’ll make steps of increasing size: 1, 2, 3.
First, you’ll try to go back from where you are (so from 0 you’d try to go to − 1) but you must obey two rules:
The new “landing site” must be greater than 0, and
The new “landing site” must be new in the sequence (it has never appeared before)
If you can’t go backwards, you go forwards.
So from 0, the next step is of size 1. If you try to go backwards, you’ll land at -1. This is against the rules, so you go forward to 1.
Now from 1, the next step is of size 2. If you try to go back, you’ll land at -1. This is against the rules, so you go forward to 3.