from collections import deque


def list3(a, b, c, *, val=0):
    return [[[val] * c for _ in range(b)] for _ in range(a)]


def neighbors4(r: int, c: int) -> list[tuple[int, int]]:
    res = []
    for dr, dc in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
        nr = r + dr
        nc = c + dc
        if not (0 <= nr < H and 0 <= nc < W): continue
        res.append((nr, nc))

    return res


INF = 1 << 60
H, W, M = map(int, input().split())
S = []
for _ in range(H):
    S.append(list(input()))


def find(c):
    for i in range(H):
        for j in range(W):
            if S[i][j] == c:
                return i, j

    assert False


sr, sc = find('S')
dists = list3(H, W, 10, val=INF)
dists[sr][sc][0] = 0
q = deque([(sr, sc, 0)])
while q:
    r, c, key = q.popleft()
    for nr, nc in neighbors4(r, c):
        if S[nr][nc] == '#': continue

        nk = key
        if S[nr][nc].islower():
            a = ord(S[nr][nc]) - ord('a') + 1
            if nk != a: continue
            if dists[nr][nc][nk] <= dists[r][c][key] + 1: continue
            dists[nr][nc][nk] = dists[r][c][key] + 1
            q.append((nr, nc, nk))
        elif S[nr][nc].isdigit():
            nk = ord(S[nr][nc]) - ord('1') + 1
            if dists[nr][nc][nk] <= dists[r][c][key] + 1: continue
            dists[nr][nc][nk] = dists[r][c][key] + 1
            q.append((nr, nc, nk))
        else:
            if dists[nr][nc][nk] <= dists[r][c][key] + 1: continue
            dists[nr][nc][nk] = dists[r][c][key] + 1
            q.append((nr, nc, nk))

gr, gc = find('G')
d = min(dists[gr][gc])
if d == INF:
    print(-1)
else:
    print(d)