dij=[[0,1],[1,0],[0,-1],[-1,0]]
dij2=[[0,2],[2,0],[0,-2],[-2,0]]
def nin():
    return list(map(int,input().split()))

import collections
h,w=nin()
s=[list(input()) for i in range(h)]
hh=2*h-1
ww=2*w-1
ss=gg=-1
black=set()
d=[-1]*(hh*ww)
for i in range(h):
    for j in range(w):
        if s[i][j]=="S":
            ss=2*i*ww+2*j
            s[i][j]="."
        elif s[i][j]=="G":
            gg=2*i*ww+2*j
            s[i][j]="."
        elif s[i][j]=="#":
            d[2*i*ww+2*j]=-2
task=collections.deque()#maxlen=hh*ww)
task.append(ss)
d[ss]=0
while len(task)>0:
    i=task.popleft()
    rin=[]
    ii,jj=i//ww,i%ww
    for di,dj in dij:
        if 0<=ii+di<hh and 0<=jj+dj<ww:
            pos=(ii+di)*ww+(jj+dj)
            if d[pos]!=-2:
                rin.append(pos)
    if ii%2==jj%2==0:
        for di,dj in dij2:
            if 0<=ii+di<hh and 0<=jj+dj<ww:
                pos=(ii+di)*ww+(jj+dj)
                if d[pos]!=-2:
                    rin.append((ii+di)*ww+(jj+dj))
    if ii%2==0 and jj%2==1:
        for di in [2,-2]:
            if 0<=ii+di<hh:
                rin.append((ii+di)*ww+(jj))
    if ii%2==1 and jj%2==0:
        for dj in [2,-2]:
            if 0<=jj+dj<ww:
                rin.append((ii)*ww+(jj+dj))
    
    for j in rin:
        if d[j]==-1:
            d[j]=d[i]+1
            #print(i,j,d[j])
            if j==gg:
                print(d[j])
                exit()
            task.append(j)