BAEKJOON 13460

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {

	static int N, M, ry, rx, by, bx;
	static char[][] map;
	static Queue<Ball> q = new LinkedList<>();
	static int[] dy = { -1, 1, 0, 0 }, dx = { 0, 0, -1, 1 };

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		N = Integer.parseInt(st.nextToken());
		M = Integer.parseInt(st.nextToken());
		map = new char[N][M];
		for (int i = 0; i < N; i++) {
			map[i] = br.readLine().toCharArray();
			for (int j = 0; j < M; j++) {
				if (map[i][j] == 'R') {
					ry = i;
					rx = j;
					map[i][j] = '.';
				} else if (map[i][j] == 'B') {
					by = i;
					bx = j;
					map[i][j] = '.';
				}
			}
		}
		q.offer(new Ball(ry, rx, by, bx, 0));
		bfs();
	}

	private static void bfs() {

		while (!q.isEmpty()) {
			Ball b = q.poll();
			if (b.cnt > 10) { // 10회 이상이므로 실패
				System.out.println(-1);
				return;
			}
			if(map[b.by][b.bx] == 'O') // 파란공이 골인한경우
				continue;
			if(map[b.ry][b.rx] == 'O') { // 빨간공이 골인한 경우
				System.out.println(b.cnt);
				return;
			}
			
			for (int i = 0; i < 4; i++) {
				by = b.by;
				bx = b.bx;
				while (true) {
					by += dy[i];
					bx += dx[i];
					if (map[by][bx] == '#') {
						by -= dy[i];
						bx -= dx[i];
						break;
					}
					if (map[by][bx] == 'O') {
						break;
					}
				}
				ry = b.ry;
				rx = b.rx;
				while (true) {
					ry += dy[i];
					rx += dx[i];
					if (map[ry][rx] == '#') {
						ry -= dy[i];
						rx -= dx[i];
						break;
					}
					if (map[ry][rx] == 'O') {
						break;
					}
				}
				if(ry == by && rx == bx && map[ry][rx] != 'O') {
					int red = Math.abs(b.ry - ry) + Math.abs(b.rx - rx);
					int blue = Math.abs(b.by - by) + Math.abs(b.bx - bx);
					
					if(red > blue) { //레드가 크면 레드가 늦게 온거
						ry -= dy[i];
						rx -= dx[i];
					}else if(blue > red) {
						by -= dy[i];
						bx -= dx[i];
					}
				}
				q.offer(new Ball(ry, rx, by, bx, b.cnt+1));
			}
		}
	}

	static class Ball {
		int ry, rx, by, bx, cnt;
		public Ball(int ry, int rx, int by, int bx, int cnt) {
			this.ry = ry;
			this.rx = rx;
			this.by = by;
			this.bx = bx;
			this.cnt = cnt;
		}
	}
}