with open('input.text', 'r') as file:
    data: list[str] = file.readlines()

topo_map = [[int(c) if c != '.' else -1 for c in line.strip()] for line in data]

x_bound: int = len(topo_map[0]) - 1
y_bound: int = len(topo_map) - 1

class Coord:
    x: int
    y: int

    def __init__(self, x: int, y: int):
        self.x = x
        self.y = y

    def __str__(self) -> str:
        return f'({self.x}, {self.y})'

def in_bounds(c: Coord) -> bool:
    if c.y > y_bound or c.y < 0:
        return False

    if c.x > x_bound or c.x < 0:
        return False

    return True

def score_trail(c: Coord, last: int | None = 0) -> int:

    if not in_bounds(c):
        return 0

    v: int = topo_map[c.y][c.x]
    if v == 9:
        return 1

    if v - last != 1 and last != 0:
        return 0

    up, down, left, right = Coord(c.x, c.y - 1), Coord(c.x, c.y + 1), Coord(c.x - 1, c.y), Coord(c.x + 1, c.y)

    dirs = []

    for dir in [up, down, left, right]:
        if in_bounds(dir):
            if topo_map[dir.y][dir.x] - v == 1:
                dirs.append(score_trail(dir, v))

    return sum(dirs)

total = 0
for y, line in enumerate(topo_map):
    for x, n in enumerate(line):
        if n == 0:
            total += score_trail(Coord(x, y))

print(total)