#include "atcoder/modint.hpp"
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;

using i32 = int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128_t;
using f64 = long double;
using p2 = pair<i64, i64>;
using el = tuple<i64, i64, i64>;
using mint = atcoder::modint1000000007;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  _main();
}

i64 pow(i64 x, i64 n, i64 m) {
  i64 res = 1;
  i64 t = x % m;
  while (n > 0) {
    if (n & 1) {
      res = res * t % m;
    }
    t = t * t % m;
    n >>= 1;
  }
  return res;
}

void _main() {
  i64 h, w, m;
  cin >> h >> w >> m;
  vector<string> s(h);
  for (i64 i = 0; i < h; i++) cin >> s[i];
  vector dp(h, vector(w, vector(m + 1, i64(1e18))));
  queue<el> que;
  for(i64 i = 0; i < h; i++) {
    for (i64 j = 0; j < w; j++) {
      if (s[i][j] != 'S') continue;
      dp[i][j][0] = 0;
      que.push({i, j, 0});
    }
  }
  while (!que.empty()) {
    auto [i, j, k] = que.front();
    que.pop();
    i64 nxt[5] = {0, 1, 0, -1, 0};
    for (i64 p = 0; p < 4; p++) {
      i64 ni = i + nxt[p], nj = j + nxt[p + 1];
      if (ni < 0 || nj < 0 || ni >= h || nj >= w || s[ni][nj] == '#') continue;
      if ('a' <= s[ni][nj] && s[ni][nj] <= 'z') {
        i64 id = s[ni][nj] - 'a' + 1;
        assert(id <= m);
        if (id != k) continue;
        if (dp[ni][nj][k] > dp[i][j][k] + 1) {
          dp[ni][nj][k] = dp[i][j][k] + 1;
          que.push({ni, nj, k});
        }
      } else if ('1' <= s[ni][nj] && s[ni][nj] <= '9') {
        i64 nk = s[ni][nj] - '0';
        assert(nk <= m);
        if (dp[ni][nj][nk] > dp[i][j][k] + 1) {
          dp[ni][nj][nk] = dp[i][j][k] + 1;
          que.push({ni, nj, nk});
        }
      } else {
        if (dp[ni][nj][k] > dp[i][j][k] + 1) {
          dp[ni][nj][k] = dp[i][j][k] + 1;
          que.push({ni, nj, k});
        }
      }
    }
  }
  i64 ans = 1e18;
  for (i64 i = 0; i < h; i++) {
    for (i64 j = 0; j < w; j++) {
      if (s[i][j] != 'G') continue;
      for (i64 k = 0; k <= m; k++) {
        ans = min(ans, dp[i][j][k]);
      }
    }
  }
  if (ans == 1e18) {
    cout << "-1\n";
  } else {
    cout << ans << "\n";
  }
}