#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

// using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

bool isin(ll x, ll y, ll H, ll W) {
    return (x >= 0 && x < H && y >= 0 && y < W);
}

int main() {
    ll H, W, M;
    cin >> H >> W >> M;
    vector<string> S(H);
    for (ll i = 0; i < H; i++) {
        cin >> S[i];
    }
    ll sx = -1;
    ll sy = -1;
    ll gx = -1;
    ll gy = -1;
    for (ll i = 0; i < H; i++) {
        for (ll j = 0; j < W; j++) {
            if (S[i][j] == 'S') {
                sx = i;
                sy = j;
            } else if (S[i][j] == 'G') {
                gx = i;
                gy = j;
            }
        }
    }
    ll INF = 10000000000023;
    vector<vector<vector<ll>>> dist(
        H, vector<vector<ll>>(W, vector<ll>(M + 1, INF)));
    queue<pair<pll, ll>> que;

    dist[sx][sy][0] = 0;
    que.push(make_pair(make_pair(sx, sy), 0));

    vector<ll> dx = {1, 0, -1, 0};
    vector<ll> dy = {0, 1, 0, -1};
    while (que.size()) {
        pair<pll, ll> pp = que.front();
        que.pop();

        ll px = pp.first.first;
        ll py = pp.first.second;
        ll key = pp.second;
        // debug_out(px, py, key);
        for (ll i = 0; i < 4; i++) {
            ll nx = px + dx[i];
            ll ny = py + dy[i];
            if (isin(nx, ny, H, W)) {
                if (S[nx][ny] == '#') {
                    continue;
                } else if (S[nx][ny] >= '1' && S[nx][ny] <= '9') {
                    ll nkey = (ll)(S[nx][ny] - '0');
                    if (dist[nx][ny][nkey] < INF) {
                        continue;
                    }
                    dist[nx][ny][nkey] = dist[px][py][key] + 1;
                    que.push(make_pair(make_pair(nx, ny), nkey));
                } else if (S[nx][ny] >= 'a' && S[nx][ny] <= 'i') {
                    ll ndr = (ll)(S[nx][ny] - 'a') + 1;
                    if (ndr != key) {
                        continue;
                    }
                    if (dist[nx][ny][key] < INF) {
                        continue;
                    }
                    dist[nx][ny][key] = dist[px][py][key] + 1;
                    que.push(make_pair(make_pair(nx, ny), key));
                } else {
                    if (dist[nx][ny][key] < INF) {
                        continue;
                    }
                    dist[nx][ny][key] = dist[px][py][key] + 1;
                    que.push(make_pair(make_pair(nx, ny), key));
                }
            }
        }
    }
    ll ans = INF;
    for (ll i = 0; i < M + 1; i++) {
        ans = min(ans, dist[gx][gy][i]);
    }

    if (ans == INF) {
        cout << -1 << endl;
    } else {
        cout << ans << endl;
    }
}