from functools import reduce
from itertools import islice


def nth(iterable, n):
    return next(islice(iter(iterable), n, n + 1))


def mult(iterable):
    return reduce(lambda x, y: x * y, iterable)


def count_trees(data, right, down):
    return [nth(row, right * idx % len(row)) for idx, row in enumerate(data[::down])].count("#")


data = list(map(str.strip, open("input")))


# Part 1
down = 1
right = 3
print(count_trees(data, right, down))


# Part 2
slopes = [
    # R, D
    [1, 1],
    [3, 1],
    [5, 1],
    [7, 1],
    [1, 2],
]
print(mult([count_trees(data, right, down) for right, down in slopes]))