from collections import deque
H, W = map(int, input().split())
board = [list(input()) for _ in range(H)]

n_move = [(-2, -1),(-2, 1),(-1, -2),(-1, 2),(1, -2),(1, 2),(2, -1),(2, 1)]
b_move = [(-1, 1),(-1, -1),(1, 1),(1, -1)]

n_reached = [[0 for _ in range(W)] for __ in range(H)]
b_reached = [[0 for _ in range(W)] for __ in range(H)]

for x in range(W):
    for y in range(H):
        if board[y][x] == 'S':
            start = (x, y)

class Piece:
    def __init__(self, state, style, step):
        self.state = state
        self.style = style
        self.step = step

def BFS(s):
    q = deque()
    q.append(Piece(s, 'knight', 0))
    while q:
        current = q.popleft()
        x, y = current.state
        form = current.style
        count = current.step
        if board[y][x] == 'G':
            return count
        if form == 'knight':
            for j, k in n_move:
                nx, ny = x + j, y + k
                if 0 > nx or nx > W-1 or 0 > ny or ny > H-1:
                    continue
                if n_reached[ny][nx] == 1:
                    continue
                n_reached[ny][nx] = 1
                if board[ny][nx] == 'R':
                    nform = 'bishop'
                else:
                    nform = 'knight'
                p = Piece((nx, ny), nform, count+1)
                q.append(p)
        else:
            for n, m in b_move:
                nx, ny = x + n, y + m
                if 0 > nx or nx > W-1 or 0 > ny or ny > H-1:
                    continue
                if b_reached[ny][nx] == 1:
                    continue
                b_reached[ny][nx] = 1
                if board[ny][nx] == 'R':
                    nform = 'knight'
                else:
                    nform = 'bishop'
                p = Piece((nx, ny), nform, count+1)
                q.append(p)
    return -1

print(BFS(start))