def move_on_trail(map_positions: list[list[int]], current_row: int, current_col: int, next_height: int) -> int:
    summits_found = 0

    row_count = len(map_positions)
    col_count = len(map_positions[0])
    for dir_row, dir_col in ((-1, 0), (1, 0), (0, -1), (0, 1)):
        next_row = current_row + dir_row
        next_col = current_col + dir_col

        if not (0 <= next_row < row_count and 0 <= next_col < col_count):
            continue

        if map_positions[next_row][next_col] == next_height:
            if next_height == 9:
                summits_found += 1
            else:
                summits_found += move_on_trail(map_positions, next_row, next_col, next_height + 1)

    return summits_found


def get_trailhead_rating(map_positions: list[list[int]], head_row: int, head_col: int) -> int:
    return move_on_trail(map_positions, head_row, head_col, 1)


data = []
with open("input") as f:
    for line in f:
        data.append([int(elem) for elem in tuple(line.strip())])

count = 0
for row, line in enumerate(data):
    for col, height in enumerate(line):
        if height == 0:
            count += get_trailhead_rating(data, row, col)

print(count)