#include <bits/stdc++.h>
using namespace std;
#define ll long long
// #define rep(i,n) for(int i=0;i<(int)n;i++)
#define rep(i,r) for(ll i=0;i<(ll)r;i++)
#define vi vector<int>
#define vl vector<ll>
#define vd vector<double>
#define vb vector<bool>
#define vs vector<string>
#define vc vector<char>
#define ull unsigned long long
#define chmax(a,b) a=max(a,b)
#define chmin(a,b) a=min(a,b)



// ll inf=(1ll<<62);

// ll rui(ll a,ll b){
//     if(b==0)return 1;
//     if(b%2==1) return a*rui(a*a,b/2);
//     return rui(a*a,b/2);
// }

// ll const mod=998244353ll;
// ll modrui(ll a,ll b){
//     if(b==0)return 1;
//     if(b%2==1) return a%mod*modrui(a%mod*a%mod,b/2)%mod;
//     return modrui(a%mod*a%mod,b/2)%mod;
// }

// ll inv(ll x){
//     return modrui(x,mod-2);
// }


void solve(){
    ll h,w,m;cin >> h >> w >> m;
    vs room(h);
    rep(i,h)cin >> room[i];

    ll dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
    vector<vector<vb>> used(h,vector<vb>(w,vb(10,0)));
    deque<array<ll,4>> dq(0);
    rep(i,h)rep(j,w)if(room[i][j]=='S'){
        dq.push_back({i,j,0,0});
        used[i][j][0]=1;
    }

    
    while(!dq.empty()){
        ll i=dq[0][0],j=dq[0][1],key=dq[0][2],d=dq[0][3];
        dq.pop_front();
        rep(k,4){
            ll ni=i+dx[k],nj=j+dy[k];
            if(0<=ni && ni<h && 0<=nj && nj<w && !used[ni][nj][key] && room[ni][nj]!='#'){
                if(room[ni][nj]=='.'){
                    dq.push_back({ni,nj,key,d+1});
                    used[ni][nj][key]=1;
                }
                else if(islower(room[ni][nj])){
                    if(key==(ll)(room[ni][nj]-'a'+1)){
                        dq.push_back({ni,nj,key,d+1});
                        used[ni][nj][key]=1;
                    }
                }
                else if(room[ni][nj]=='G'){
                    cout << d+1 << endl;
                    return;
                }
                else if(room[ni][nj]!='S'){//数字
                    dq.push_back({ni,nj,room[ni][nj]-'0',d+1});
                    used[ni][nj][key]=1;
                    used[ni][nj][room[ni][nj]-'0']=1;
                }
            }
        }
    }
    cout << -1 << endl;
}



int main(){
    ll t=1;
    // cin >> t;
    while(t--)solve();
}