red and black

red_and_black.py

BLACK = "."
RED = "#"
HUMAN = "@"
DIRECTIONS = [(-1, 0), (0, 1), (1, 0), (0, -1)]  # up right down left


def red_and_black(col, row, point, graph):
    stack = [point]
    cnt = 0
    while stack:
        y, x = stack.pop()
        if graph[y][x] == RED:
            continue

        cnt += 1
        graph[y][x] = RED

        for dy, dx in DIRECTIONS:
            if 0 <= y + dy < row and 0 <= x + dx < col and graph[y + dy][x + dx] == BLACK:
                stack.append((y + dy, x + dx))
    return cnt


while True:
    col, row = map(int, input().split())
    if col == 0 and row == 0: break

    graph = []
    x, y = -1, -1
    for i in range(row):
        line = input()
        graph.append(list(line))
        if (idx := line.find(HUMAN)) != -1:
            y, x = i, idx

    print(red_and_black(col, row, (y, x), graph))