H,W,M = map(int,input().split())

S = [ input() for i in range(H) ]

INF = float("inf")

dp = [ [ [INF] * 10 for j in range(W)] for i in range(H)]

st = None
go = None
for i in range(H):
    for j in range(W):
        if S[i][j] == "S":
            st = (i,j)
        if S[i][j] == "G":
            go = (i,j)

from collections import deque
q = deque()

dp[st[0]][st[1]][0] = 0
q.append( (st[0],st[1],0) )

while q:

    x,y,z = q.popleft()
    cost = dp[x][y][z] + 1
    
    for i,j in ( (x-1,y),(x+1,y),(x,y-1),(x,y+1) ):

        if not ( 0 <= i < H and 0 <= j < W ):
            continue
        
        elif S[i][j] == "#":
            pass

        elif S[i][j] == "." or S[i][j] == "G" or S[i][j] == "S":
            if dp[i][j][z] > cost:
                dp[i][j][z] = cost
                q.append( (i,j,z) )

            if S[i][j] == "G":
                break

        elif "1" <= S[i][j] <= "9":
            k = int(S[i][j])
            if dp[i][j][k] > cost:
                dp[i][j][k] = cost
                q.append( (i,j,k) )

        elif "a" <= S[i][j] <= "i":
            k = ord(S[i][j]) - ord("a") + 1
            if z == k and dp[i][j][k] > cost:
                dp[i][j][k] = cost
                q.append( (i,j,k) )

#for k in range(10):
#   for i in range(H):
#        print ( [ dp[i][j][k] for j in range(W) ] )
#    print ()

ans = min(dp[go[0]][go[1]])
if ans == INF:
    ans = -1

print (ans)