#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
const int dx[4] = { 1,0,-1,0 };
const int dy[4] = { 0,-1,0,1 };
int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int h, w, m;
	cin >> h >> w >> m;
	vector<string>s(h);
	rep(i, h)cin >> s[i];
	P st, ed;
	rep(i, h)rep(j, w) {
		if (s[i][j] == 'S')st = { i,j };
		else if (s[i][j] == 'G')ed = { i,j };
	}
	vector dp(h, vector(w, vector(10, INF)));
	dp[st.first][st.second][0] = 0;
	queue<array<int, 3>>que;
	que.push({ st.first,st.second,0 });
	while (!que.empty()) {
		auto[x, y, t] = que.front();
		que.pop();
		rep(i, 4) {
			int nx = x + dx[i];
			int ny = y + dy[i];
			int nval = dp[x][y][t] + 1;
			if (nx < 0 || nx >= h)continue;
			if (ny < 0 || ny >= w)continue;
			if (s[nx][ny] == '#')continue;
			if ('1' <= s[nx][ny] && s[nx][ny] <= '9') {
				int nt = s[nx][ny] - '0';
				if (chmin(dp[nx][ny][nt], nval)) {
					que.push({ nx,ny,nt });
				}
			}
			else if ('a' <= s[nx][ny] && s[nx][ny] <= 'i') {
				int nk = s[nx][ny] - 'a' + 1;
				if (nk != t)continue;
				if (chmin(dp[nx][ny][t], nval)) {
					que.push({ nx,ny,t });
				}
			}
			else {
				if (chmin(dp[nx][ny][t], nval)) {
					que.push({ nx,ny,t });
				}
			}
		}
	}
	int ans = INF;
	rep(i, 10)chmin(ans, dp[ed.first][ed.second][i]);
	if (ans == INF)ans = -1;
	cout << ans << endl;
	return 0;
}