// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")


#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;(i)<(n);(i)++)
#define REP(i,a,n) for(ll i=(a);(i)<(n);(i)++)
#define rrep(i,n) for(ll i=(n)-1;(i)>=(0ll);(i)--)
#define RREP(i,a,n) for(ll i=(n)-1;(i)>=(a);(i)--)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define be(v) (v).begin(),(v).end()
#define all(v) (v).begin(),(v).end()
#define foa(i,v) for(auto& (i) : (v))
#define UQ(v) sort(be(v)), (v).erase(unique(be(v)), (v).end())
#define UQ2(v,cmp) sort(be(v)), (v).erase(unique(be(v),cmp), (v).end())
#define UQ3(v,cmp) sort(be(v),cmp), (v).erase(unique(be(v)), (v).end())
#define UQ4(v,cmp,cmp2) sort(be(v), cmp), (v).erase(unique(be(v),cmp2), (v).end())
#define LB(x,v) (lower_bound(be(v),(x))-(v).begin())
#define LB2(x,v,cmp) (lower_bound(be(v),(x),(cmp))-(v).begin())
#define UB(x,v) (upper_bound(be(v),(x))-(v).begin())
#define UB2(x,v,cmp) (upper_bound(be(v),(x),(cmp))-(v).begin())
#define dout()  cout << fixed << setprecision(20)
#define randinit() srand((unsigned)time(NULL))

template<class T, class U> bool chmin(T& t, const U& u) { if (t > u){ t = u; return 1;} return 0; }
template<class T, class U> bool chmax(T& t, const U& u) { if (t < u){ t = u; return 1;} return 0; }


ll Rnd(ll L=0, ll R=mod99){return rand()%(R-L)+L;}



void solve(){
	ll h,w,m;
	cin >> h >> w >> m;
	V<string> v(h);
	rep(i,h) cin >> v[i];
	VVV<ll> dist(m+1, VV<ll>(h, V<ll>(w, INF)));
	queue<tuple<ll,ll,ll>> que;
	ll gx, gy;
	rep(i, h) rep(j, w){
		if(v[i][j] == 'S'){
			que.push({0, i, j});
			dist[0][i][j] = 0;
		}
		if(v[i][j] == 'G'){
			gx = i, gy = j;
		}
	}
	V<ll> dx={0,1,0,-1}, dy={1,0,-1,0};
	while(!que.empty()){
		auto[a,x,y] = que.front();
		que.pop();
		if(v[x][y] == '#') continue;
		if('1' <= v[x][y] and v[x][y] <= '9' and v[x][y] - '0' != a){
			if(chmin(dist[v[x][y]-'0'][x][y], dist[a][x][y])){
				que.push({v[x][y] - '0', x, y});
			}
			continue;
		}
		
		rep(i, 4){
			ll nx = x+dx[i];
			ll ny = y+dy[i];
			if(nx < 0 or ny < 0 or nx >= h or ny >= w) continue;
			if(v[nx][ny] == '#') continue;
			if('a' <= v[x][y] and v[x][y] <= 'i' and v[x][y] - 'a' != a-1) continue;
			if(chmin(dist[a][nx][ny], dist[a][x][y]+1)) que.push({a, nx, ny});
		}
	}
	ll ans = INF;
	rep(i, m+1) chmin(ans, dist[i][gx][gy]);
	if(ans == INF) ans = -1;
	cout << ans << endl;
	
    
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t=1;
    // cin >> t;
    rep(i,t) solve();
}