#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    int h, w, m; cin >> h >> w >> m;
    vector<string> s(h); for(int i=0; i<h; i++) cin >> s[i];

    int si, sj, gi, gj;
    for(int i=0; i<h; i++){
        for(int j=0; j<w; j++){
            if(s[i][j] == 'S') si = i, sj = j;
            if(s[i][j] == 'G') gi = i, gj = j;
        }
    }

    vector<vector<vector<int>>> dist(h, vector<vector<int>>(w, vector<int>(m+1, -1)));
    queue<tuple<int, int, int>> que;
    dist[si][sj][m] = 0;
    que.emplace(si, sj, m);
    int di[4] = {1, 0, -1, 0};
    int dj[4] = {0, 1, 0, -1};
    while(!que.empty()){
        auto [i, j, k] = que.front(); que.pop();
        for(int d=0; d<4; d++){
            int ni = i + di[d];
            int nj = j + dj[d];
            if(ni < 0 || ni >= h || nj < 0 || nj >= w) continue;
            if(s[ni][nj] == '#') continue;

            if('a' <= s[ni][nj] && s[ni][nj] <= 'z'){
                if(k != (int)(s[ni][nj]-'a')) continue;
                if(dist[ni][nj][k] != -1) continue;
                dist[ni][nj][k] = dist[i][j][k] + 1;
                que.emplace(ni, nj, k);
            }else if('1' <= s[ni][nj] && s[ni][nj] <= '9'){
                if(dist[ni][nj][s[ni][nj]-'0'-1] != -1) continue;
                dist[ni][nj][s[ni][nj]-'0'-1] = dist[i][j][k] + 1;
                que.emplace(ni, nj, (int)(s[ni][nj]-'0')-1);
            }else{
                if(dist[ni][nj][k] != -1) continue;
                dist[ni][nj][k] = dist[i][j][k] + 1;
                que.emplace(ni, nj, k);
            }
        }
    }

    int ans = -1;
    for(int i=0; i<=m; i++){
        if(dist[gi][gj][i] == -1) continue;
        if(ans == -1 || ans > dist[gi][gj][i]) ans = dist[gi][gj][i];
    }

    cout << ans << endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}