## \-\-\- Day 23: A Long Walk ---

The Elves resume water filtering operations! Clean water starts flowing over the edge of Island Island.

They offer to help _you_ go over the edge of Island Island, too! Just hold on tight to one end of this impossibly long rope and they'll lower you down a safe distance from the massive waterfall you just created.

As you finally reach Snow Island, you see that the water isn't really reaching the ground: it's being _absorbed by the air_ itself. It looks like you'll finally have a little downtime while the moisture builds up to snow-producing levels. Snow Island is pretty scenic, even without any snow; why not take a walk?

There's a map of nearby hiking trails (your puzzle input) that indicates _paths_ ( `.`), _forest_ ( `#`), and steep _slopes_ ( `^`, `>`, `v`, and `<`).

For example:

```
#.#####################
#.......#########...###
#######.#########.#.###
###.....#.>.>.###.#.###
###v#####.#v#.###.#.###
###.>...#.#.#.....#...#
###v###.#.#.#########.#
###...#.#.#.......#...#
#####.#.#.#######.#.###
#.....#.#.#.......#...#
#.#####.#.#.#########v#
#.#...#...#...###...>.#
#.#.#v#######v###.###v#
#...#.>.#...>.>.#.###.#
#####v#.#.###v#.#.###.#
#.....#...#...#.#.#...#
#.#########.###.#.#.###
#...###...#...#...#.###
###.###.#.###v#####v###
#...#...#.#.>.>.#.>.###
#.###.###.#.###.#.#v###
#.....###...###...#...#
#####################.#

```

You're currently on the single path tile in the top row; your goal is to reach the single path tile in the bottom row. Because of all the mist from the waterfall, the slopes are probably quite _icy_; if you step onto a slope tile, your next step must be _downhill_ (in the direction the arrow is pointing). To make sure you have the most scenic hike possible, _never step onto the same tile twice_. What is the longest hike you can take?

In the example above, the longest hike you can take is marked with `O`, and your starting position is marked `S`:

```
#S#####################
#OOOOOOO#########...###
#######O#########.#.###
###OOOOO#OOO>.###.#.###
###O#####O#O#.###.#.###
###OOOOO#O#O#.....#...#
###v###O#O#O#########.#
###...#O#O#OOOOOOO#...#
#####.#O#O#######O#.###
#.....#O#O#OOOOOOO#...#
#.#####O#O#O#########v#
#.#...#OOO#OOO###OOOOO#
#.#.#v#######O###O###O#
#...#.>.#...>OOO#O###O#
#####v#.#.###v#O#O###O#
#.....#...#...#O#O#OOO#
#.#########.###O#O#O###
#...###...#...#OOO#O###
###.###.#.###v#####O###
#...#...#.#.>.>.#.>O###
#.###.###.#.###.#.#O###
#.....###...###...#OOO#
#####################O#

```

This hike contains `94` steps. (The other possible hikes you could have taken were `90`, `86`, `82`, `82`, and `74` steps long.)

Find the longest hike you can take through the hiking trails listed on your map. _How many steps long is the longest hike?_