/**
	author:  shobonvip
	created: 2025.07.12 05:30:47
**/

#include<bits/stdc++.h>
using namespace std;

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)
#define all(v) v.begin(), v.end()

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int h, w, m;
	cin >> h >> w >> m;
	vector<string> s(h);
	rep(i,0,h) cin >> s[i];


	int sx = -1, sy = -1;
	int gx = -1, gy = -1;
	rep(i,0,h) rep(j,0,w) {
		if (s[i][j] == 'S') {
			sx = i;
			sy = j;
		}else if (s[i][j] == 'G') {
			gx = i;
			gy = j;
		}
	}

	vector d(10, vector(h, vector<int>(w,1e9)));
	d[0][sx][sy] = 0;
	deque<tuple<int,int,int>> mada;
	mada.push_back({0,sx,sy});
	while(!mada.empty()) {
		auto [typ,i,j] = mada.front();
		mada.pop_front();
		for (auto[x,y]: {
			pair(i-1,j),
			pair(i+1,j),
			pair(i,j-1),
			pair(i,j+1)
		}){
			if(!(0<=x&&x<h))continue;
			if(!(0<=y&&y<w))continue;
			if(s[x][y]=='#')continue;
			int ntyp=typ;
			if('1'<=s[x][y]&&s[x][y]<='9') {
				ntyp=int(s[x][y]-'0');
			}
			if('a'<=s[x][y]&&s[x][y]<='i'){
				if(typ-1 != int(s[x][y]-'a')) continue;
			}
			if(chmin(d[ntyp][x][y],d[typ][i][j]+1)){
				mada.push_back({ntyp,x,y});
			}

		}
	}

	int ans=1e9;
	rep(i,0,10){
		chmin(ans,d[i][gx][gy]);
	}
	if(ans>1e8){
		cout<<-1<<'\n';
	}else{
		cout<<ans<<'\n';
	}
}