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: