import sys
input = sys.stdin.readline

from collections import deque

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

MAP=[input().strip() for i in range(H)]

DP=[[[1<<60]*W for i in range(H)] for j in range(10)]


Q=deque()

for i in range(H):
    for j in range(W):
        if MAP[i][j]=="S":
            DP[0][i][j]=0
            Q.append((0,i,j))

while Q:
    #print(Q)
    kk,x,y=Q.popleft()

    now=DP[kk][x][y]

    for z,w in [(x+1,y),(x-1,y),(x,y+1),(x,y-1)]:
        if 0<=z<H and 0<=w<W:
            if MAP[z][w]=="#":
                continue
            #print(MAP[z][w])

            if 49<=ord(MAP[z][w])<=57:
                key=ord(MAP[z][w])-48

                if DP[key][z][w]>now+1:
                    DP[key][z][w]=now+1
                    Q.append((key,z,w))
                    
            elif 97<=ord(MAP[z][w])<=122:
                key=ord(MAP[z][w])-96

                if kk==key:
                    if DP[key][z][w]>now+1:
                        DP[key][z][w]=now+1
                        Q.append((key,z,w))

            else:
                if DP[kk][z][w]>now+1:
                    DP[kk][z][w]=now+1
                    Q.append((kk,z,w))

ANS=1<<60

for i in range(H):
    for j in range(W):
        if MAP[i][j]=="G":
            for kk in range(10):
                ANS=min(ANS,DP[kk][i][j])

if ANS>10**6:
    print(-1)
else:
    print(ANS)