You've almost reached the exit of the cave, but the walls are getting closer together. Your submarine can barely still fit, though; the main problem is that the walls of the cave are covered in [chitons](https://en.wikipedia.org/wiki/Chiton), and it would be best not to bump any of them.

The cavern is large, but has a very low ceiling, restricting your motion to two dimensions. The shape of the cavern resembles a square; a quick scan of chiton density produces a map of *risk level* throughout the cave (your puzzle input). For example:

```
1163751742
1381373672
2136511328
3694931569
7463417111
1319128137
1359912421
3125421639
1293138521
2311944581

```

You start in the top left position, your destination is the bottom right position, and you cannot move diagonally. The number at each position is its *risk level*; to determine the total risk of an entire path, add up the risk levels of each position you *enter* (that is, don't count the risk level of your starting position unless you enter it; leaving it adds no risk to your total).

Your goal is to find a path with the *lowest total risk*. In this example, a path with the lowest total risk is highlighted here:

```
1163751742
1381373672
2136511328
3694931569
7463417111
1319128137
1359912421
3125421639
1293138521
2311944581

```

The total risk of this path is `*40*` (the starting position is never entered, so its risk is not counted).

*What is the lowest total risk of any path from the top left to the bottom right?*

To begin, [get your puzzle input](15/input).

Answer: