#include <bits/stdc++.h>
#include <atcoder/segtree>
using namespace std;
template <class F> class y_combinator {
    F f;

   public:
    y_combinator(F&& f) : f(std::forward<F>(f)) {}
    template <class... Args> auto operator()(Args&&... args) const { return f(*this, std::forward<Args>(args)...); }
};
using ll = long long;
using ld = long double;
template <class T, class U = std::less<T>> using prique = std::priority_queue<T, std::vector<T>, U>;
template <class T> T floor(T a, T b) noexcept { return a / b - (a % b && (a ^ b) < 0); }
template <class T> T ceil(T a, T b) noexcept { return floor(a + b - 1, b); }
template <class T> bool chmin(T& x, const T& y) noexcept { return (x > y ? x = y, true : false); }
template <class T> bool chmax(T& x, const T& y) noexcept { return (x < y ? x = y, true : false); }
#define overload4(a, b, c, d, e, ...) e
#define rep1(a) for (long long _i = 0; _i < (a); _i++)
#define rep2(i, a) for (long long i = 0; i < (a); i++)
#define rep3(i, a, b) for (long long i = (a); i < (b); i++)
#define rep4(i, a, b, c) for (long long i = (a); i < (b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(i, a, b, c) for (long long i = (a); i > (b); i += (c))
#define all(x) std::begin(x), std::end(x)
#define rall(x) std::rbegin(x), std::rend(x)
#define pb push_back
#ifndef LOCAL
#define debug(...)
#endif

void run_case() {
    int H, W, M;
    cin >> H >> W >> M;
    vector<string> S(H);
    rep(i, H) cin >> S[i];

    vector dp(H, vector(W, vector<int>(M + 1, 1e9)));
    auto find = [&](char s) -> pair<int, int> {
        rep(i, H) rep(j, W) if (S[i][j] == s) {
            return {i, j};
        }
        assert(0);
    };

    auto st = find('S');
    auto go = find('G');
    dp[st.first][st.second][0] = 0;
    queue<array<int, 3>> que;
    que.push({st.first, st.second, 0});
    const int dx[] = {0, 1, 0, -1, 0};
    while (!que.empty()) {
        auto [i, j, k] = que.front();
        que.pop();
        rep(r, 4) {
            int ni = i + dx[r], nj = j + dx[r + 1];
            if (ni < 0 || nj < 0 || ni >= H || nj >= W) continue;
            if (S[ni][nj] == '#') continue;
            if ('a' <= S[ni][nj] && S[ni][nj] <= 'i') {
                if (S[ni][nj] - 'a' + 1 != k) continue;
                if (chmin(dp[ni][nj][k], dp[i][j][k] + 1)) {
                    que.push({ni, nj, k});
                }
            } else if ('1' <= S[ni][nj] && S[ni][nj] <= '9') {
                int ch = S[ni][nj] - '0';
                if (chmin(dp[ni][nj][ch], dp[i][j][k] + 1)) {
                    que.push({ni, nj, ch});
                }
            } else {
                if (chmin(dp[ni][nj][k], dp[i][j][k] + 1)) {
                    que.push({ni, nj, k});
                }
            }
        }
    }
    int ans = 1e9;
    rep(i, M + 1) {
        // cout << "i = " << i << endl;
        chmin(ans, dp[go.first][go.second][i]);
        // rep(j, H) rep(k, W) cout << dp[j][k][i] << " \n"[k == W - 1];
    }
    cout << (ans == 1e9 ? -1 : ans) << "\n";
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::fixed(std::cout).precision(16);
    int T = 1;
    // cin >> T;
    while (T--) run_case();
    return 0;
}