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

using ll =long long;


void solve(){
   
    ll H,W,M;
    cin>>H>>W>>M;
    vector<string> B(H);
    ll SY,SX,GY,GX;
    for(int i=0;i<H;i++){
        cin>>B[i];
        for(int j=0;j<W;j++){
            if(B[i][j]=='S'){
                SY=i;
                SX=j;
            }
            if(B[i][j]=='G'){
                GY=i;
                GX=j;
            }
        }
    }
    vector<vector<vector<ll>>> DP(H,vector<vector<ll>>(W,vector<ll>(10,1e18)));
    DP[SY][SX][0]=0;
    queue<array<ll,3>> Q;
    Q.push({SY,SX,0});
    vector<ll> nd={0,1,0,-1,0};
    while(!Q.empty()){
        auto [y,x,k]=Q.front();
        Q.pop();
        for(int d=0;d<4;d++){
            ll ny=y+nd[d];
            ll nx=x+nd[d+1];
            ll nk=k;
            if(ny<0||nx<0||ny>=H||nx>=W)continue;
            if(B[ny][nx]=='#')continue;
            if('a'<=B[ny][nx]&&B[ny][nx]<='z'){
                if(B[ny][nx]-'a'+1!=k)continue;
            }
            if('1'<=B[ny][nx]&&B[ny][nx]<='9'){
                nk=B[ny][nx]-'0';
            }
            if(DP[ny][nx][nk]>DP[y][x][k]+1){
                DP[ny][nx][nk]=DP[y][x][k]+1;
                Q.push({ny,nx,nk});
            }

        }
    }
    ll an=1e18;
    for(int i=0;i<10;i++)an=min(an,DP[GY][GX][i]);
    cout<<(an<1e17?an:-1)<<endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T=1;
    // cin>>T;
    while(T--)solve();
}