// #pragma GCC target("avx")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
using namespace std;

using std::cin;
using std::cout;

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
bool chmax(T &a, const T b) {if(a<b) {a=b; return true;} else {return false;}}
template<typename T>
bool chmin(T &a, const T b) {if(a>b) {a=b; return true;} else {return false;}}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

void solve() {
    int h, w, n;
    cin >> h >> w >> n;
    int stx, sty, glx, gly;
    vector<string> s(h);
    FOR(h) {
        cin >> s[i];
        rep(j, w) {
            if (s[i][j] == 'S') stx = i, sty = j;
            if (s[i][j] == 'G') glx = i, gly = j;
        }
    }
    vector dist(h, vector(w, vector<int>(10, -1)));
    dist[stx][sty][0] = 0;
    queue<tuple<int, int, int>> que;
    que.emplace(stx, sty, 0);
    while (!que.empty()) {
        auto [x, y, k] = que.front();
        que.pop();
        rep(d, 4) {
            int nx = x + dx[d];
            int ny = y + dy[d];
            if (nx < 0 || ny < 0 || nx >= h || ny >= w) continue;
            if (s[nx][ny] == '#') continue;
            if ('a' <= s[nx][ny] && s[nx][ny] <= 'i' && k != (s[nx][ny] - 'a' + 1)) continue;
            int nk = k;
            if ('1' <= s[nx][ny] && s[nx][ny] <= '9') nk = (s[nx][ny] - '0');
            if (dist[nx][ny][nk] < 0) {
                dist[nx][ny][nk] = dist[x][y][k] + 1;
                que.emplace(nx, ny, nk);
            }
        }
    }
    int ans = INF;
    rep(i, 10) if (dist[glx][gly][i] != -1) chmin(ans, dist[glx][gly][i]);
    cout << (ans == INF? -1 : ans) << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}