def get_adjacent_tiles(grid, j, i):
    deltas = (-1, 0, 1)
    prev_tiles, adjacent_tiles = [], ""

    for i_delta in deltas:
        for j_delta in deltas:
            i_delta = 0 if i == 0 and i_delta < 0 else i_delta
            j_delta = 0 if j == 0 and j_delta < 0 else j_delta

            if i_delta == j_delta == 0:
                continue
            elif (j + j_delta, i + i_delta) in prev_tiles:
                continue

            try:
                adjacent_tiles += grid[j + j_delta][i + i_delta]
                prev_tiles.append((j + j_delta, i + i_delta))
            except:
                pass

    return adjacent_tiles

@timer
def process_v1(data, too_many_rolls=4, tile_tracking=False):
    tiles = {"empty": ".", "roll": "@"}
    grid = [list(lane) for lane in data]
    reachable_rolls, reachable_tiles = 0, []
    tiles_per_lane, total_lanes = len(grid[0]), len(grid)

    for i in range(tiles_per_lane):
        for j in range(total_lanes):
            if grid[j][i] == tiles["empty"]:
                continue

            adjacent_tiles = get_adjacent_tiles(grid, j, i)
            if adjacent_tiles.count(tiles["roll"]) < too_many_rolls:
                reachable_rolls += 1
                reachable_tiles.append((j, i))

    if tile_tracking:
        return reachable_rolls, reachable_tiles
    else:
        return reachable_rolls

@timer
def process_v2(data):
    tiles = {"empty": ".", "roll": "@"}
    done = False
    reachable_rolls = 0
    grid = [list(lane) for lane in data]

    while not done:
        new_reachable_rolls, new_reachable_tiles = process_v1(grid, tile_tracking=True)
        reachable_rolls += new_reachable_rolls

        for tile in new_reachable_tiles:
            grid[tile[0]][tile[1]] = tiles["empty"]

        if new_reachable_rolls == 0:
            done = True

    return reachable_rolls