import sys
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#####################################################################

h, w = na()
s = [input() for i in range(h)]

from collections import deque

for i in range(h):
    for j in range(w):
        if s[i][j] == "S":
            sx, sy = i, j
        elif s[i][j] == "G":
            gx, gy = i, j

def f(x, y, z):
    return x * 3 * w + y * 3 + z

dist = [-1] * (h * w * 3)

dq = deque([(sx, sy, 0)])
dist[f(sx, sy, 0)] = 0

while dq:
    x, y, i = dq.popleft()
    
    if i == 0:
        for dx, dy in [[1, 0], [0, 1], [-1, 0], [0, -1]]:
            nx = x + dx
            ny = y + dy
            if not (0 <= nx < h and 0 <= ny < w):
                continue
            
            if s[nx][ny] != "#" and dist[f(nx, ny, 0)] == -1:
                dist[f(nx, ny, 0)] = dist[f(x, y, 0)] + 1
                dq.append((nx, ny, 0))

                
        for dx, dy in [[1, 0], [-1, 0]]:
            nx = x + dx
            ny = y + dy
            if not (0 <= nx < h and 0 <= ny < w):
                continue
            if dist[f(nx, ny, 1)] == -1:
                dist[f(nx, ny, 1)] = dist[f(x, y, 0)] + 1
                dq.append((nx, ny, 1))

        for dx, dy in [[0, 1], [0, -1]]:
            nx = x + dx
            ny = y + dy
            if not (0 <= nx < h and 0 <= ny < w):
                continue
            if dist[f(nx, ny, 2)] == -1:
                dist[f(nx, ny, 2)] = dist[f(x, y, 0)] + 1
                dq.append((nx, ny, 2))
    elif i == 1:
        for dx, dy in [[0, 1], [0, -1]]:
            nx = x + dx
            ny = y + dy
            if not (0 <= nx < h and 0 <= ny < w):
                continue
            if dist[f(nx, ny, 1)] == -1:
                dist[f(nx, ny, 1)] = dist[f(x, y, i)] + 1
                dq.append((nx, ny, 1))
        if dist[f(x, y, 0)] == -1 and s[x][y] != "#":
            dist[f(x, y, 0)] = dist[f(x, y, i)] + 1
            dq.append((x, y, 0))
        if dist[f(x, y, 2)] == -1:
            dist[f(x, y, 2)] = dist[f(x, y, i)] + 1
            dq.append((x, y, 2))
        
    else:
        for dx, dy in [[1, 0], [-1, 0]]:
            nx = x + dx
            ny = y + dy
            if not (0 <= nx < h and 0 <= ny < w):
                continue
            if dist[f(nx, ny, 2)] == -1:
                dist[f(nx, ny, 2)] = dist[f(x, y, i)] + 1
                dq.append((nx, ny, 2))
        if dist[f(x, y, 0)] == -1 and s[x][y] != "#":
            dist[f(x, y, 0)] = dist[f(x, y, i)] + 1
            dq.append((x, y, 0))
        if dist[f(x, y, 1)] == -1:
            dist[f(x, y, 1)] = dist[f(x, y, i)] + 1
            dq.append((x, y, 1))

# for i in range(h):
#     print([dist[f(i, j, 0)] for j in range(w)])
# print()
# for i in range(h):
#     print([dist[f(i, j, 1)] for j in range(w)])
# print()
# for i in range(h):
#     print([dist[f(i, j, 2)] for j in range(w)])


print(dist[f(gx, gy, 0)])