\--- Day 1: Inverse Captcha ---
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The night before Christmas, one of Santa's Elves calls you in a panic. "The printer's broken! We can't print the *Naughty or Nice List*!" By the time you make it to sub-basement 17, there are only a few minutes until midnight. "We have a big problem," she says; "there must be almost *fifty* bugs in this system, but nothing else can print The List. Stand in this square, quick! There's no time to explain; if you can convince them to pay you in *stars*, you'll be able to--" She pulls a lever and the world goes blurry.

When your eyes can focus again, everything seems a lot more pixelated than before. She must have sent you inside the computer! You check the system clock: *25 milliseconds* until midnight. With that much time, you should be able to collect all *fifty stars* by December 25th.

Collect stars by solving puzzles. Two puzzles will be made available on each ~~day~~ millisecond in the Advent calendar; the second puzzle is unlocked when you complete the first. Each puzzle grants *one star*. Good luck!

You're standing in a room with "digitization quarantine" written in LEDs along one wall. The only door is locked, but it includes a small interface. "Restricted Area - Strictly No Digitized Users Allowed."

It goes on to explain that you may only leave by solving a [captcha](https://en.wikipedia.org/wiki/CAPTCHA) to prove you're *not* a human. Apparently, you only get one millisecond to solve the captcha: too fast for a normal human, but it feels like hours to you.

The captcha requires you to review a sequence of digits (your puzzle input) and find the *sum* of all digits that match the *next* digit in the list. The list is circular, so the digit after the last digit is the *first* digit in the list.

For example:

* `1122` produces a sum of `3` (`1` + `2`) because the first digit (`1`) matches the second digit and the third digit (`2`) matches the fourth digit.
* `1111` produces `4` because each digit (all `1`) matches the next.
* `1234` produces `0` because no digit matches the next.
* `91212129` produces `9` because the only digit that matches the next one is the last digit, `9`.

*What is the solution* to your captcha?

Your puzzle answer was `1182`.

\--- Part Two ---
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You notice a progress bar that jumps to 50% completion. Apparently, the door isn't yet satisfied, but it did emit a *star* as encouragement. The instructions change:

Now, instead of considering the *next* digit, it wants you to consider the digit *halfway around* the circular list. That is, if your list contains `10` items, only include a digit in your sum if the digit `10/2 = 5` steps forward matches it. Fortunately, your list has an even number of elements.

For example:

* `1212` produces `6`: the list contains `4` items, and all four digits match the digit `2` items ahead.
* `1221` produces `0`, because every comparison is between a `1` and a `2`.
* `123425` produces `4`, because both `2`s match each other, but no other digit has a match.
* `123123` produces `12`.
* `12131415` produces `4`.

*What is the solution* to your new captcha?

Your puzzle answer was `1152`.

Both parts of this puzzle are complete! They provide two gold stars: \*\*

At this point, all that is left is for you to [admire your Advent calendar](/2017).

If you still want to see it, you can [get your puzzle input](1/input).