Baekjoon-13460-구슬 탈출 2

N,M = map(int,input().split())
board = []
balls = {}
for i in range(N):
    line = [c for c in input().strip()]
    board.append(line)
    for j in range(len(line)):
        if line[j] in ['R','B']:
            balls[line[j]] = [i,j]
            board[i][j] = '.'

# Backtracking
def tilt(dirs, balls):
    # dirs 0-right 1-up 2-left 3-down
    dx, dy = [[1,0],[0,1],[-1,0],[0,-1]][dirs]
    rx,ry = balls['R']
    bx,by = balls['B']
    reached = []
    new_balls = {}
    for color, [x,y] in balls.items():
        while 0<=x+dx<N and 0<=y+dy<M:
            if board[x+dx][y+dy] == '#':
                break
            elif board[x+dx][y+dy] == 'O':
                x += dx
                y += dy
                reached.append(color)
                break
            x += dx
            y += dy
        new_balls[color] = [x,y]
    if new_balls['R'] == new_balls['B']:
        if (rx-bx)*dx < 0:
            new_balls['R'][0] -= dx
        elif (rx-bx)*dx > 0:
            new_balls['B'][0] -= dx
        if (ry-by)*dy < 0:
            new_balls['R'][1] -= dy
        elif (ry-by)*dy > 0:
            new_balls['B'][1] -= dy
    
    if new_balls['R']==[rx,ry] and new_balls['B']==[bx,by]:
        return -1,{}

    if 'B' in reached:
        return -1, {}
    elif 'R' in reached:
        return 1, {}
    else:
        return 0, new_balls

def solve(tries, balls):
    if tries == 11:
        return 11
    else:
        new_tries = []
        for i in range(4):
            res, new_balls = tilt(i, balls)
            if res == 1:
                return tries
            if res == 0:
                new_tries.append(new_balls)
        if len(new_tries) == 0:
            return 11
        else:
            return min([solve(tries+1,bs) for bs in new_tries])

result = solve(1,balls)
if result == 11:
    print(-1)
else:
    print(result)