#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
const int di[] = {1, 0, -1, 0};
const int dj[] = {0, 1, 0, -1};

int dist[500][500][10];

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, m;
  cin >> h >> w >> m;
  constexpr int INF = 1001001001;
  rep(i, h) rep(j, w) rep(k, m + 1) dist[i][j][k] = INF;
  vector<string> s(h);
  rep(i, h) cin >> s[i];
  int si, sj, ti, tj;
  rep(i, h) rep(j, w) {
    if (s[i][j] == 'S') {
      si = i, sj = j;
      s[i][j] = '.';
    } else if (s[i][j] == 'G') {
      ti = i, tj = j;
      s[i][j] = '.';
    }
  }
  deque<tuple<int, int, int, int>> q;
  dist[si][sj][0] = 0;
  q.emplace_back(si, sj, 0, 0);
  auto idxchk = [&](int i, int j) { return 0 <= i && i < h && 0 <= j && j < w; };
  while (q.size()) {
    auto [i, j, k, d] = q.front(); q.pop_front();
    if (dist[i][j][k] != d) continue;
    if ('1' <= s[i][j] && s[i][j] <= '9' && k != s[i][j] - '0') {
      int nk = s[i][j] - '0';
      if (chmin(dist[i][j][nk], d)) q.emplace_front(i, j, nk, d);
      continue;
    } else if ('a' <= s[i][j] && s[i][j] <= 'i' && k != s[i][j] - 'a' + 1) {
      continue;
    }
    rep(dir, 4) {
      int ni = i + di[dir], nj = j + dj[dir];
      if (!idxchk(ni, nj) || s[ni][nj] == '#') continue;
      if (chmin(dist[ni][nj][k], d + 1)) q.emplace_back(ni, nj, k, d + 1);
    }
  }
  int ans = INF;
  rep(k, m + 1) chmin(ans, dist[ti][tj][k]);
  if (ans == INF) ans = -1;
  cout << ans << '\n';
}