from collections import deque
def roll(direction,red,blue):
global arr,visited
stack = deque()
red = [*red,True]
blue = [*blue,True]
stack.append((red,blue))
while stack:
r,b = stack.popleft()
r_x,r_y,r_state = r
b_x,b_y,b_state = b
visited[r_x][r_y] = False
if r_state:
nr_x = r_x + dx[direction]
nr_y = r_y + dy[direction]
if 0<=nr_x<N and 0<=nr_y<M:
if nr_x == b_x and nr_y == b_y:
if not b_state:
r_state = False
else:
if arr[nr_x][nr_y] == '#':
r_state = False
elif arr[nr_x][nr_y] == 'O':
r_state = False
r_x = -1
r_y = -1
else:
r_x = nr_x
r_y = nr_y
if b_state:
nb_x = b_x + dx[direction]
nb_y = b_y + dy[direction]
if 0<=nb_x<N and 0<=nb_y<M:
if nb_x == r_x and nb_y == r_y:
if not r_state:
b_state = False
else:
if arr[nb_x][nb_y] == '#':
b_state = False
elif arr[nb_x][nb_y] == 'O':
b_state = False
b_x = -1
b_y = -1
else:
b_x = nb_x
b_y = nb_y
if not r_state and not b_state:
if b_x == -1:
return -1
if r_x == -1:
return 1
return [r_x,r_y,b_x,b_y]
stack.append(([r_x,r_y,r_state],[b_x,b_y,b_state]))
def bfs(r,b,g):
global arr
stack = deque()
stack.append((r,b,0))
visited[r[0]][r[1]] = False
while stack:
red,blue,cnt = stack.popleft()
if cnt >= 10:
return -1
for i in range(4):
nx = red[0] + dx[i]
ny = red[1] + dy[i]
if 0<=nx<N and 0<=ny<M:
result = roll(i,red,blue)
if type(result) == int:
if result == 1:
return cnt+1
else:
nr = [result[0],result[1]]
nb = [result[2],result[3]]
stack.append((nr,nb,cnt+1))
return -1
dx = [-1,1,0,0]
dy = [0,0,-1,1]
N,M = map(int,input().split())
arr = []
red_ball = []
blue_ball = []
goal = []
visited = [[True]*M for _ in range(N)]
for x in range(N):
temp = list(input())
for y in range(M):
if temp[y] == 'R':
temp[y] = '.'
red_ball = [x,y]
elif temp[y] == 'B':
temp[y] = '.'
blue_ball = [x,y]
elif temp[y] == 'O':
goal = [x,y]
arr.append(temp)
print(bfs(red_ball,blue_ball,goal))