#include <bits/stdc++.h>
using namespace std;
constexpr int MOD = 998244353;
constexpr int MD = 1000000007;
constexpr int INF = INT_MAX;
constexpr long long LINF = LLONG_MAX;
#define REP(i, n) for (int i = 0; i < (int)(n); i++)
using ll = long long;using vi = vector<int>;using vll = vector<ll>;
template <class T>
using ps = pair<T, T>;
template <class T>
using vec = vector<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;  // ascendent

template <typename T>
int sz(const T& x) { return x.size(); }

// a = min(a,b)
template <typename T, typename S>
inline bool chmin(T& a, const S& b) {
  return (a > b ? a = b, 1 : 0);
}
template <typename T, typename S>
inline bool chmax(T& a, const S& b) {
  return (a < b ? a = b, 1 : 0);
}

ll mpow(int base, int exponent, int mod){
    if(exponent == 0) return 1;
    ll c = mpow(base, exponent/2, mod);
    c *= c;
    c %= mod;
    if(exponent % 2 == 1){
        c *= base;
        c %= mod;
    }
    return c;
}

/* 
auto push = [&](int r, int c){
    if(r < 0 || c < 0 || r >= h || c >= w) return;
    if(dist[r][c] != -1) return;
};
*/ //dfs/bfs埋め込み用

/*
class edge{
public:
    int to, weight;
    edge(int a, int b){
        to = a; weight = b;
    }
};
*/ //template of edge
/*class edge2{
public:
    int from, to, weight;
    edge2(int w, int a, int b){
        from = w; to = a; weight = b;
    }
};
bool comp(edge2 a, edge2 b){
    return a.weight < b.weight;
}
*/ //template of edge2
struct before_main_function {
  before_main_function() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
    std::cout << setprecision(20) << fixed;
#define endl "\n"
  }
} before_main_function;
vec<int > d, l;
vec<vec<int>> g;
void dfs(int p){
  for(auto it : g[p]){
    d[it] = max(d[p], l[it]);
    dfs(it);
  }
}
int main(int /*argc*/, char** /*argv*/){
  int h, w;
  std::cin >> h >> w;
  vec<vec<int>> a(h, vec<int>(w, -1));
  REP(i, h-1){
    REP(j, w){
      std::cin >> a[i+1][j];
    }
  }
  ll ans = INF;
  vec<vec<int>> d(h, vec<int>(w, INF));
  pqg<pair<ll, pair<int, int>>> pq;
  const vec<vec<int>> dir = {{0, 1}, {0, -1}, {1, 1}, {1, -1}, {1, 0}, {-1, 0}, {-1, 1}, {-1, -1}};
  for(int i = 1; i < h-1; i++){
    if(a[i][0] == -1) continue;
    //dijkstra 目的地は a[なんとか][w-1]
    pq.emplace(a[i][0], make_pair(i, 0));
    while(!pq.empty()){
      auto it = pq.top(); pq.pop();
      const pair<int, int> from = it.second;
      if(d[from.first][from.second] < it.first) continue;
      for(auto nd : dir){
        if(nd[0]+from.first < 0 || nd[0]+from.first >= h) continue;
        if(nd[1]+from.second < 0 || nd[1]+from.second >= w) continue;
        if(a[nd[0]+from.first][nd[1]+from.second] == -1) continue;
        const ll c = it.first+a[nd[0]+from.first][nd[1]+from.second];
        if(c < d[nd[0]+from.first][nd[1]+from.second]){
          d[nd[0]+from.first][nd[1]+from.second] = c;
          pq.emplace(c, make_pair(nd[0]+from.first, nd[1]+from.second));
        }
      }
    }
  }
  for(int i = 1; i < h-1; i++){
    chmin(ans, d[i][w-1]);
  }
  if(ans == INF) cout << "-1\n";
  else std::cout << ans << endl;
  return 0;
}