// With the toboggan login problems resolved, you set off toward the airport. While travel by toboggan might be easy, it's certainly not safe: there's very minimal steering and the area is covered in trees. You'll need to see which angles will take you near the fewest trees.
// Due to the local geology, trees in this area only grow on exact integer coordinates in a grid. You make a map (your puzzle input) of the open squares (.) and trees (#) you can see. For example:
// ..##.......
// #...#...#..
// .#....#..#.
// ..#.#...#.#
// .#...##..#.
// ..#.##.....
// .#.#.#....#
// .#........#
// #.##...#...
// #...##....#
// .#..#...#.#
// These aren't the only trees, though; due to something you read about once involving arboreal genetics and biome stability, the same pattern repeats to the right many times:
// You start on the open square (.) in the top-left corner and need to reach the bottom (below the bottom-most row on your map).
// The toboggan can only follow a few specific slopes (you opted for a cheaper model that prefers rational numbers); start by counting all the trees you would encounter for the slope right 3, down 1:
// From your starting position at the top-left, check the position that is right 3 and down 1. Then, check the position that is right 3 and down 1 from there, and so on until you go past the bottom of the map.
// The locations you'd check in the above example are marked here with O where there was an open square and X where there was a tree:
// Time to check the rest of the slopes - you need to minimize the probability of a sudden arboreal stop, after all.
// Determine the number of trees you would encounter if, for each of the following slopes, you start at the top-left corner and traverse the map all the way to the bottom:
// Right 1, down 1.
// Right 3, down 1. (This is the slope you already checked.)
// Right 5, down 1.
// Right 7, down 1.
// Right 1, down 2.
// In the above example, these slopes would find 2, 7, 3, 4, and 2 tree(s) respectively; multiplied together, these produce the answer 336.
// What do you get if you multiply together the number of trees encountered on each of the listed slopes?