abc088d.py

H, W = map(int, input().split())
maze = []
distances = []
n_aisle = 0
for i in range(H):
    row = input()
    maze.append(row)
    distances.append([100000000 for i in range(W)])
    n_aisle += row.count('.')
 
distances[0][0] = 0
directions = [(1, 0), (-1, 0), (0, 1), (0, -1)]
 
visited = [(0, 0)]
queue = [(0, 0)]
while len(queue) > 0:
    y, x = queue.pop(0)
    for dy, dx in directions:
        y2, x2 = y + dy, x + dx
        if y2 < 0 or y2 >= H or x2 < 0 or x2 >= W:
            continue
        if (y2, x2) in visited:
            continue
        if maze[y2][x2] == '.':
            distances[y2][x2] = distances[y][x] + 1
            visited.append((y2, x2))
            queue.append((y2, x2))
 
if distances[H - 1][W - 1] == 100000000:
    print(-1)
else:
    print(n_aisle - distances[H - 1][W - 1] - 1)