15653.py

# 구슬 탈출 4
import sys

input = sys.stdin.readline

N, M = map(int, input().split())

visit = [[[[0] * M for _ in range(N)] for __ in range(M)] for ___ in range(N)]

board = []

for i in range(N):
    line = input().rstrip()
    for j in range(M):
        if line[j] == "R":
            R = [i, j]
            line = line.replace("R", ".")
        if line[j] == "B":
            B = [i, j]
            line = line.replace("B", ".")
    board.append(line)


def moveR(y, x):
    for i in range(x + 1, M):
        m = board[y][i]
        if m == "O":
            return -1
        elif m == "#":
            return [y, i - 1]


def moveL(y, x):
    for i in range(x - 1, -1, -1):
        m = board[y][i]
        if m == "O":
            return -1
        elif m == "#":
            return [y, i + 1]


def moveU(y, x):
    for i in range(y - 1, -1, -1):
        m = board[i][x]
        if m == "O":
            return -1
        elif m == "#":
            return [i + 1, x]


def moveD(y, x):
    for i in range(y + 1, N):
        m = board[i][x]
        if m == "O":
            return -1
        elif m == "#":
            return [i - 1, x]


cur = [[R, B]]
end = False
i = 0
while True:
    i += 1
    next = []
    while cur:
        R, B = cur.pop()
        Ry, Rx = R
        By, Bx = B
        if visit[Ry][Rx][By][Bx]:
            continue
        R_R = moveR(Ry, Rx)
        R_L = moveL(Ry, Rx)
        R_U = moveU(Ry, Rx)
        R_D = moveD(Ry, Rx)
        B_R = moveR(By, Bx)
        B_L = moveL(By, Bx)
        B_U = moveU(By, Bx)
        B_D = moveD(By, Bx)

        if B_R != -1:
            if R_R == -1:
                end = True
                print(i)
                break
            else:
                if R_R == B_R:
                    if Rx < Bx:
                        R_R[1] -= 1
                    else:
                        B_R[1] -= 1
                next.append([R_R, B_R])
        if B_L != -1:
            if R_L == -1:
                end = True
                print(i)
                break
            else:
                if R_L == B_L:
                    if Rx < Bx:
                        B_L[1] += 1
                    else:
                        R_L[1] += 1
                next.append([R_L, B_L])
        if B_U != -1:
            if R_U == -1:
                end = True
                print(i)
                break
            else:
                if R_U == B_U:
                    if Ry < By:
                        B_U[0] += 1
                    else:
                        R_U[0] += 1
                next.append([R_U, B_U])
        if B_D != -1:
            if R_D == -1:
                end = True
                print(i)
                break
            else:
                if R_D == B_D:
                    if Ry < By:
                        R_D[0] -= 1
                    else:
                        B_D[0] -= 1
                next.append([R_D, B_D])

        visit[Ry][Rx][By][Bx] = 1
    if not next:
        break
    cur += next
    if end == True:
        break
if not end:
    print(-1)