#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using VS = vector<string>;
using P = pair<ll,ll>;
using VP = vector<P>;
#define rep(i, n) for (ll i = 0; i < ll(n); i++)
#define out(x) cout << x << endl
#define dout(x) cout << fixed << setprecision(10) << x << endl
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define sz(x) (int)(x.size())
#define re0 return 0
#define pcnt __builtin_popcountll
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr int inf = 1e9;
constexpr ll INF = 1e18;
//using mint = modint1000000007;
using mint = modint998244353;
int di[4] = {1,0,-1,0};
int dj[4] = {0,1,0,-1};

int main(){
    ll h,w;
    cin >> h >> w;
    VVL a(h,VL(w,ll(1e10)));
    for(int i = 1;i < h-1;i++)rep(j,w){
        cin >> a[i][j];
        if(a[i][j] == -1) a[i][j] = ll(1e10);
    }
    auto id = [&](int i,int j,bool in){
        if(in) return i*w+j;
        else return i*w+j+h*w;
    };
    int si = 2*h*w;
    int gi = si+1;
    mf_graph<ll> g(2*h*w+2);
    rep(i,h)rep(j,w){
        g.add_edge(id(i,j,1),id(i,j,0),a[i][j]);
        rep(v,4){
            int ni = i+di[v];
            int nj = j+dj[v];
            if(ni < 0 || nj < 0 || ni >= h || nj >= w) continue;
            g.add_edge(id(ni,nj,0),id(i,j,1),ll(1e10));
        }
    }
    rep(j,w) g.add_edge(si,id(0,j,1),ll(1e10));
    rep(j,w) g.add_edge(id(h-1,j,0),gi,ll(1e10));
    ll ans = g.flow(si,gi);
    if(ans >= ll(1e10)) ans = -1;
    out(ans);
}