#include <bits/stdc++.h>
using namespace std;
// #include <atcoder/modint>
// using namespace atcoder;
// using mint = modint998244353;
using ll = long long;
#define fix(x) fixed << setprecision(x)
#define rep(i, n) for(int i = 0; i < n; ++i)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}
constexpr ll INFLL = (1LL << 62), MOD = 998244353;
constexpr int INF = (1 << 30);
int H[] = {0,1,0,-1}, W[] = {1,0,-1,0};
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int h,w,m;
    cin >> h >> w >> m;
    vector<string> s(h);
    int sh = -1, sw = -1, gh = -1, gw = -1;
    rep(i,h){
        cin >> s[i];
        rep(j,w){
            if(s[i][j]=='S') sh = i, sw = j;
            if(s[i][j]=='G') gh = i, gw = j;
        }
    }
    vector dist(h,vector(w,vector<int>(m+1,INF)));
    dist[sh][sw][m] = 0;
    queue<tuple<int,int,int>> que;
    que.emplace(sh,sw,m);
    while(que.size()){
        auto [p,q,x] = que.front();
        que.pop();
        rep(i,4){
            int np = p+H[i], nq = q+W[i];
            if(np<0 || np>=h || nq<0 || nq>=w || s[np][nq]=='#') continue;
            if(s[np][nq]>='a' && s[np][nq]<='i' && s[np][nq]-'a'!=x) continue;
            int y = x;
            if(s[np][nq]>='1' && s[np][nq]<='9') y = s[np][nq] - '1';
            if(chmin(dist[np][nq][y], dist[p][q][x]+1)) que.emplace(np,nq,y);
        }
    }
    int ans = INF;
    rep(i,m+1) chmin(ans, dist[gh][gw][i]);
    if(ans==INF) ans = -1;
    cout << ans << '\n';
    return 0;
}