#include <iostream>
#include <vector>
#include <queue>
using namespace std;
typedef long long ll;
typedef pair<ll,int> pll;
vector<pll> G[4000100]; //weight,vertex
priority_queue<pll,vector<pll>,greater<pll>> que;
ll d[4000100],INF = 100000000000000000;
void add_edge(int from,int to,ll weight){ G[from].push_back({weight,to}); 
    // if(to==13) cout << from << " " << to << " " << weight << endl;
}
void dijkstra(int s){
    que.push({0,s});
    while(que.size()){
        pll p = que.top(); que.pop();
        ll dis = p.first,pos = p.second;
        if(d[pos]!=INF) continue;
        d[pos] = dis;
        for(auto e:G[pos]){
            if(d[e.second]==INF) que.push({dis + e.first,e.second});
        }
    }
}

int a[1010][1010];
int dx[8] = {1,1,0,-1,-1,-1,0,1};
int dy[8] = {0,1,1,1,0,-1,-1,-1};
bool ch(int h,int w,int nx,int ny){
    if(nx<0 || nx>=h || ny<0 || ny>=w || a[nx][ny]==-1) return false;
    return true;
}

int mp(int w,int nx,int ny){
    return w*nx + ny;
}

int main(){
    int i,j,k,h,w; cin >> h >> w;
    for(i=0;i<h - 2;i++){
        for(j=0;j<w;j++){
            cin >> a[i][j];
        }
    }
    for(i=0;i<h - 2;i++){
        for(j=0;j<w;j++){
            if(a[i][j]==-1) continue;
            for(k=0;k<8;k++){
                int nx = i + dx[k],ny = j + dy[k];
                if(!ch(h - 2,w,nx,ny)) continue;
                add_edge(mp(w,i,j),mp(w,nx,ny),a[i][j]);
            }
        }
    }
    int s = (h - 2)*w;
    int t = (h - 2)*w + 1;
    for(i=0;i<=t;i++) d[i] = INF;
    for(i=0;i<h - 2;i++){
        if(a[i][0]!=-1) add_edge(s,mp(w,i,0),0);
        if(a[i][w - 1]!=-1) add_edge(mp(w,i,w - 1),t,a[i][w - 1]);
    }
    dijkstra(s);
    if(d[t]!=INF) cout << d[t] << "\n";
    else cout << -1 << "\n";
    // for(i=0;i<(h - 2)*w;i++){
    //     cout << d[i] << " ";
    //     if(i%w==w - 1) cout << "\n";
    // }
    // cout << d[s] << " " << d[t] << endl;
}