As you approach the rings of Saturn, your ship's *low fuel* indicator turns on. There isn't any fuel here, but the rings have plenty of raw material. Perhaps your ship's Inter-Stellar Refinery Union brand *nanofactory* can turn these raw materials into fuel.

You ask the nanofactory to produce a list of the *reactions* it can perform that are relevant to this process (your puzzle input). Every reaction turns some quantities of specific *input chemicals* into some quantity of an *output chemical*. Almost every *chemical* is produced by exactly one reaction; the only exception, `ORE`, is the raw material input to the entire process and is not produced by a reaction.

You just need to know how much `*ORE*` you'll need to collect before you can produce one unit of `*FUEL*`.

Each reaction gives specific quantities for its inputs and output; reactions cannot be partially run, so only whole integer multiples of these quantities can be used. (It's okay to have leftover chemicals when you're done, though.) For example, the reaction `1 A, 2 B, 3 C => 2 D` means that exactly 2 units of chemical `D` can be produced by consuming exactly 1 `A`, 2 `B` and 3 `C`. You can run the full reaction as many times as necessary; for example, you could produce 10 `D` by consuming 5 `A`, 10 `B`, and 15 `C`.

Suppose your nanofactory produces the following list of reactions:

```
10 ORE => 10 A
1 ORE => 1 B
7 A, 1 B => 1 C
7 A, 1 C => 1 D
7 A, 1 D => 1 E
7 A, 1 E => 1 FUEL

```

The first two reactions use only `ORE` as inputs; they indicate that you can produce as much of chemical `A` as you want (in increments of 10 units, each 10 costing 10 `ORE`) and as much of chemical `B` as you want (each costing 1 `ORE`). To produce 1 `FUEL`, a total of *31* `ORE` is required: 1 `ORE` to produce 1 `B`, then 30 more `ORE` to produce the 7 + 7 + 7 + 7 = 28 `A` (with 2 extra `A` wasted) required in the reactions to convert the `B` into `C`, `C` into `D`, `D` into `E`, and finally `E` into `FUEL`. (30 `A` is produced because its reaction requires that it is created in increments of 10.)

Or, suppose you have the following list of reactions:

```
9 ORE => 2 A
8 ORE => 3 B
7 ORE => 5 C
3 A, 4 B => 1 AB
5 B, 7 C => 1 BC
4 C, 1 A => 1 CA
2 AB, 3 BC, 4 CA => 1 FUEL

```

The above list of reactions requires *165* `ORE` to produce 1 `FUEL`:

* Consume 45 `ORE` to produce 10 `A`.
* Consume 64 `ORE` to produce 24 `B`.
* Consume 56 `ORE` to produce 40 `C`.
* Consume 6 `A`, 8 `B` to produce 2 `AB`.
* Consume 15 `B`, 21 `C` to produce 3 `BC`.
* Consume 16 `C`, 4 `A` to produce 4 `CA`.
* Consume 2 `AB`, 3 `BC`, 4 `CA` to produce 1 `FUEL`.

Here are some larger examples:

* *13312* `ORE` for 1 `FUEL`:

  ```
  157 ORE => 5 NZVS
  165 ORE => 6 DCFZ
  44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL
  12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ
  179 ORE => 7 PSHF
  177 ORE => 5 HKGWZ
  7 DCFZ, 7 PSHF => 2 XJWVT
  165 ORE => 2 GPVTF
  3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT

  ```

* *180697* `ORE` for 1 `FUEL`:

  ```
  2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG
  17 NVRVD, 3 JNWZP => 8 VPVL
  53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL
  22 VJHF, 37 MNCFX => 5 FWMGM
  139 ORE => 4 NVRVD
  144 ORE => 7 JNWZP
  5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC
  5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV
  145 ORE => 6 MNCFX
  1 NVRVD => 8 CXFTF
  1 VJHF, 6 MNCFX => 4 RFSQX
  176 ORE => 6 VJHF

  ```

* *2210736* `ORE` for 1 `FUEL`:

  ```
  171 ORE => 8 CNZTR
  7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
  114 ORE => 4 BHXH
  14 VRPVC => 6 BMBT
  6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
  6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
  15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
  13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
  5 BMBT => 4 WPTQ
  189 ORE => 9 KTJDG
  1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
  12 VRPVC, 27 CNZTR => 2 XDBXC
  15 KTJDG, 12 BHXH => 5 XCVML
  3 BHXH, 2 VRPVC => 7 MZWV
  121 ORE => 7 VRPVC
  7 XCVML => 6 RJRHP
  5 BHXH, 4 VRPVC => 5 LTCX

  ```

Given the list of reactions in your puzzle input, *what is the minimum amount of `ORE` required to produce exactly 1 `FUEL`?*

Your puzzle answer was `1582325`.

\--- Part Two ---
----------

After collecting `ORE` for a while, you check your cargo hold: *1 trillion* (*1000000000000*) units of `ORE`.

*With that much ore*, given the examples above:

* The 13312 `ORE`-per-`FUEL` example could produce *82892753* `FUEL`.
* The 180697 `ORE`-per-`FUEL` example could produce *5586022* `FUEL`.
* The 2210736 `ORE`-per-`FUEL` example could produce *460664* `FUEL`.

Given 1 trillion `ORE`, *what is the maximum amount of `FUEL` you can produce?*

Your puzzle answer was `2267486`.

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

At this point, you should [return to your Advent calendar](/2019) and try another puzzle.

If you still want to see it, you can [get your puzzle input](14/input).