from collections import deque
H,W,M=map(int,input().split())
S=[input() for _ in range(H)]
for h in range(H):
    for w in range(W):
        if S[h][w]=="S":s=(h,w)
        elif S[h][w]=="G":g=(h,w)
def pack(h, w, cnt, key, k):
    return h*(k**3)+w*(k**2)+cnt*k+key
def unpack(v, k):
    return v//(k**3), v%(k**3)//(k**2), v%(k**2)//k, v%k
K=500
vis=set()
Q=deque([pack(s[0],s[1],0,0,K)])
while Q:
    h,w,cnt,key=unpack(Q.popleft(),K)
    vis.add((h,w))
    if (h,w)==g:exit(print(cnt))
    if "1"<=S[h][w]<="9":key=int(S[h][w])
    for dh,dw in ((-1,0),(1,0),(0,-1),(0,1)):
        if not (0<=h+dh<H and 0<=w+dw<W):continue
        if S[h+dh][w+dw]=="#":continue
        if (h+dh,w+dw) in vis:continue
        if "a"<=S[h+dh][w+dw]<="i" and ord(S[h+dh][w+dw])-ord("a")+1!=key:continue
        Q.append(pack(h+dh,w+dw,cnt+1,key,K))
print(-1)