Sept. 18-24 – $20k in total prizes!

Missmarettaphotography, CC BY-SA 4.0

You’ve just landed a job re-shelving books in the Bastion’s library!

As an initiate to the Lineup of Masters, you’ve been assigned to return books
in the library. Due to a severely outdated system, the floor on which
each book is to be re-shelved comes as a sequence of commands. A `+`

represents
ascending a floor, while a `-`

represents descending a floor.

Your master requires all initiates to keep track of the position of any command in a sequence that would cause them to enter the library’s restricted section—floor -1 or lower.

The library is very large and you will never find the top or bottom floors.

The returns room, where books are received and prepared for re-shelving, and from which all sequences of commands are assumed to start, is located in the basement (floor 0).

To ensure books are re-shelved accurately and in a timely fashion, determine a way to know the (1-indexed) position of each command that will cause you to enter the restricted section.

```
-+-++---
```

```
1
3
7
```

`-`

tells you to go from floor 0 to floor -1.`+`

tells you to go from floor -1 to floor 0.`-`

tells you to go from floor 0 to floor -1.`+`

tells you to go from floor -1 to floor 0.`+`

tells you to go from floor 0 to floor 1.`-`

tells you to go from floor 1 to floor 0.`-`

tells you to go from floor 0 to floor -1.`-`

tells you to go from floor -1 to floor -2.

Commands 1, 3, and 7 caused you to enter the restricted section (go from floor 0 to floor -1).

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