#include <iostream>
#include <iomanip>//小数点出力用
//cout << fixed << setprecision(10) << ans;
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
using ll = long long;
using namespace std;
#define modPHash (ll)((1LL<<61)-1)
#define modP (ll)998244353
bool chkrng0idx(int pos, int sup) { return (0 <= pos && pos < sup); }
int clk4(int num) { return (num - 2) * (num % 2); }
void yn(bool tf) { cout << (tf ? "Yes\n" : "No\n"); }

int P[200000];
int S[200000];

void init() {
    for (int i = 0;i < 200000;i++) {
        P[i] = -1;
        S[i] = 1;
    }
}

int find(int x) {
    if (P[x] == -1) {
        return x;
    }
    else {
        P[x] = find(P[x]);
        return P[x];
    }
}

ll unite(int x, int y) {
    int a = find(x);
    int b = find(y);
    if (a != b) {
        P[b] = a;
        S[a] += S[b];
        return (ll)((ll)(S[a] - S[b]) * (ll)S[b]);
    }
    return 0;
}


int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int H, W;
    cin >> H >> W;
    int M;
    cin >> M;
    string F[500];
    vector<pair<int, int>>doors(M);
    vector<pair<int, int>>keys(M);
    queue<pair<int, pair<int, int>>>Q;
    int GX, GY;
    int dist[10][500][500];
    for (int i = 0;i < 10;i++)for (int j = 0;j < 500;j++)for (int k = 0;k < 500;k++)dist[i][j][k] = 1e9;
    for (int i = 0;i < H;i++) {
        cin >> F[i];
        for (int j = 0;j < W;j++) {
            if (F[i][j] == 'S') {
                Q.push({ 0,{i,j} });
                dist[0][i][j] = 0;
            }
            if (F[i][j] == 'G') {
                GX = i;
                GY = j;
            }
        }
    }
    while (!Q.empty()) {
        int nowK = Q.front().first;
        int X = Q.front().second.first;
        int Y = Q.front().second.second;
        Q.pop();
        for (int r = 0;r < 4;r++) {
            if (chkrng0idx(X + clk4(r), H) && chkrng0idx(Y + clk4(r + 1), W)) {
                int newK = nowK;
                if (0 <= F[X + clk4(r)][Y + clk4(r + 1)] - 0x30 && F[X + clk4(r)][Y + clk4(r + 1)] - 0x30 <= 9) {
                    newK = F[X + clk4(r)][Y + clk4(r + 1)] - 0x30;
                }
                if (F[X + clk4(r)][Y + clk4(r + 1)] != '#' && dist[newK][X + clk4(r)][Y + clk4(r + 1)] == 1e9) {
                    if (0x30 <= F[X + clk4(r)][Y + clk4(r + 1)] && F[X + clk4(r)][Y + clk4(r + 1)] <= 0x39) {
                        dist[newK][X + clk4(r)][Y + clk4(r + 1)] = dist[nowK][X][Y] + 1;
                        Q.push({ newK,{X + clk4(r), Y + clk4(r + 1)} });
                    }
                    else if (0x60 <= F[X + clk4(r)][Y + clk4(r + 1)] && F[X + clk4(r)][Y + clk4(r + 1)] <= 0x69) {
                        if (F[X + clk4(r)][Y + clk4(r + 1)] - 0x60 == nowK) {
                            dist[nowK][X + clk4(r)][Y + clk4(r + 1)] = dist[nowK][X][Y] + 1;
                            Q.push({ nowK,{X + clk4(r), Y + clk4(r + 1)} });
                        }
                    }
                    else {
                        dist[nowK][X + clk4(r)][Y + clk4(r + 1)] = dist[nowK][X][Y] + 1;
                        Q.push({ nowK,{X + clk4(r), Y + clk4(r + 1)} });
                    }
                }
            }
        }
    }
    int ans = 1e9;
    for (int i = 0;i <= M;i++) {
        ans = min(ans, dist[i][GX][GY]);
    }
    if (ans == 1e9) {
        ans = -1;
    }
    cout << ans;
}