#ifndef ONLINE_JUDGE
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#include <cassert>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
//using mint = modint1000000007;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repu(i, s, t) for (int i = (int)(s); i < (int)(t); i++)
#define repd(i, s, t) for (int i = (int)(s)-1; i >= (int)(t); i--)
#define all(v) v.begin(), v.end()
void _u() { cerr << endl; } template <class H, class... T> void _u(H&& h, T&&... t) { cerr << h << ", "; _u(move(t)...); }
#define U(...) { cerr << #__VA_ARGS__ << ": "; _u(__VA_ARGS__); }
template<typename T> bool chmax(T &a, const T b) { if(a >= b) return false; a = b; return true; }
template<typename T> bool chmin(T &a, const T b) { if(a <= b) return false; a = b; return true; }
template<typename T> istream& operator>>(istream &in, vector<T> &a) { for(T &x: a) in >> x; return in; }
template<typename T> ostream& operator<<(ostream &out, const vector<T> &a) { for(const T &x: a) out << x << ' '; return out; }
const int di[] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const int dj[] = {0, 1, 0, -1, -1, 1, 1, -1, 0};


int main() {
    int h, w, m;
    cin >> h >> w >> m;
    m++;
    auto id = [&](int i, int j, int k) { return h*w*k + w*i + j; };
    vector<string> s(h);
    cin >> s;

    vector<vector<int>> g(h*w*m);
    rep(i, h) rep(j, w) rep(k, m) rep(t, 4) {
        int ni = i + di[t];
        int nj = j + dj[t];
        int nk = k;
        if(ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
        if(s[ni][nj] == '#') continue;
        if(s[ni][nj] >= 'a' && s[ni][nj] <= 'z' && s[ni][nj] != 'a' + k - 1) continue;
        if(s[ni][nj] >= '1' && s[ni][nj] <= '9') nk = s[ni][nj] - '0';
        g[id(i, j, k)].push_back(id(ni, nj, nk));
    }

    int si, sj, gi, gj;
    rep(i, h) rep(j, w) {
        if(s[i][j] == 'S') si = i, sj = j;
        if(s[i][j] == 'G') gi = i, gj = j;
    }

    const int INF = 1e9;
    vector<int> dist(h*w*m, INF);
    queue<int> wait;
    dist[id(si, sj, 0)] = 0;
    wait.push(id(si, sj, 0));
    while(!wait.empty()) {
        int pos = wait.front(); wait.pop();
        for(int to: g[pos]) {
            if(dist[to] < INF) continue;
            dist[to] = dist[pos] + 1;
            wait.push(to);
        }
    }

    int ans = INF;
    rep(k, m) chmin(ans, dist[id(gi, gj, k)]);
    cout << (ans < INF ? ans : -1) << endl;
    return 0;
}