#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,n) for (int i=0;i<(int)(n);i++)

int main(){
  int h,w;
  cin>>h>>w;
  vector<vector<int>> a(h-2,vector<int>(w));
  rep(i,h-2) rep(j,w) cin>>a.at(i).at(j);
  vector<vector<ll>> dp(h-2,vector<ll>(w+1,1e18));
  priority_queue<pair<ll,pair<int,int>>,vector<pair<ll,pair<int,int>>>,greater<pair<ll,pair<int,int>>>> q;
  rep(i,h-2) if(a.at(i).at(0)!=-1) q.push({a.at(i).at(0),{i,0}});
  vector<int> dx={0,1,0,-1,1,-1,-1,1};
  vector<int> dy={1,0,-1,0,1,1,-1,-1};
  auto isok=[&](int x,int y){
    return 0<=x&&x<h-2&&0<=y&&y<w;
  };
  while(!q.empty()){
    auto [sc,p]=q.top();
    q.pop();
    auto [x,y]=p;
    if(dp.at(x).at(y)!=1e18) continue;
    dp.at(x).at(y)=sc;
    rep(i,8){
      int nx=x+dx.at(i);
      int ny=y+dy.at(i);
      if(isok(nx,ny)&&a.at(nx).at(ny)!=-1) q.push({sc+a.at(nx).at(ny),{nx,ny}});
    }
  }
  ll ans=1e18;
  rep(i,h-2){
    ans=min(ans,dp.at(i).at(w-1));
  }
  if(ans==1e18) ans=-1;
  cout<<ans<<endl;
}