/* -*- coding: utf-8 -*-
 *
 * 3199.cc:  No.3199 Key-Door Grid - yukicoder
 */

#include<cstdio>
#include<queue>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_H = 500;
const int MAX_W = 500;
const int MAX_M = 9;
const int MAX_HW = MAX_H * MAX_W;
const int MAX_GN = MAX_HW * (MAX_M + 1);
const int dxs[] = { 1, 0, -1, 0 }, dys[] = { 0, -1, 0, 1 };

/* typedef */

using qi = queue<int>;

/* global variables */

char fs[MAX_HW + 4];
int ds[MAX_GN];

/* subroutines */

/* main */

int main() {
  int h, w, m;
  scanf("%d%d%d", &h, &w, &m);
  int hw = h * w; m++;
  for (int i = 0; i < h; i++) scanf("%s", fs + i * w);

  int st = -1, gl = -1;
  for (int i = 0; i < hw; i++) {
    if (fs[i] == 'S') st = i;
    else if (fs[i] == 'G') gl = i;
  }
  //printf(" st=%d, gl=%d\n", st, gl);

  int gn = hw * m;
  fill(ds, ds + gn, -1);
  ds[st * m] = 0;
  qi q;
  q.push(st * m);

  int gd = -1;
  while (! q.empty()) {
    auto u = q.front(); q.pop();
    int up = u / m, uk = u % m;
    int uy = up / w, ux = up % w;
    //printf(" %d,%d,%d\n", uy, ux, uk);

    if (up == gl) {
      gd = ds[u];
      break;
    }

    for (int di = 0; di < 4; di++) {
      int vy = uy + dys[di], vx = ux + dxs[di], vp = vy * w + vx;
      if (vy >= 0 && vy < h && vx >= 0 && vx < w && fs[vp] != '#') {
	if (fs[vp] >= 'a' && fs[vp] <= 'i' && fs[vp] - 'a' + 1 != uk)
	  continue;

	int vk = (fs[vp] >= '1' && fs[vp] <= '9') ? fs[vp] - '0' : uk;
	int v = vp * m + vk;
	if (ds[v] < 0) ds[v] = ds[u] + 1, q.push(v);
      }
    }
  }

  printf("%d\n", gd);
  
  return 0;
}