#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  int H,W;
  cin>>H>>W;
  H -= 2;
  vector<vector<int>> A(H,vector<int>(W));
  for(int i=0;i<H;i++)for(int j=0;j<W;j++){
  	cin>>A[i][j];
  	if(A[i][j] == -1) A[i][j] = 1e18;
  } 
  vector<vector<pair<int,int>>> G(H*W);
  vector<int> dist(H*W,1e18);
  for(int i=0;i<H;i++)for(int j=0;j<W;j++){
  	if(i != 0) G[i*W+j].push_back({(i-1)*W+j,A[i-1][j]});
  	if(j != 0) G[i*W+j].push_back({(i)*W+j-1,A[i][j-1]});
  	if(i != H-1) G[i*W+j].push_back({(i+1)*W+j,A[i+1][j]});
  	if(j != W-1) G[i*W+j].push_back({(i)*W+j+1,A[i][j+1]});
  	if(i != 0 && j != 0) G[i*W+j].push_back({(i-1)*W+j-1,A[i-1][j-1]});
  	if(j != 0 && i != H-1) G[i*W+j].push_back({(i+1)*W+j-1,A[i+1][j-1]});
  	if(i != 0 && j != W-1) G[i*W+j].push_back({(i-1)*W+j+1,A[i-1][j+1]});
  	if(j != W-1 && i != H-1) G[i*W+j].push_back({(i+1)*W+j+1,A[i+1][j+1]});
  }
  priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> pq;
  for(int i=0;i<H;i++){
  	dist[i*W] = A[i][0];
  	pq.push({dist[i*W],i*W});
  }
  while(!pq.empty()){
  	int u,w;
  	tie(w,u) = pq.top();
  	pq.pop();
  	if(dist[u] != w) continue;
  	for(auto y:G[u]){
  		int v,x;
  		tie(v,x) = y;
  		if(dist[v] <= w+x) continue;
  		dist[v] = w+x;
  		pq.push({dist[v],v});
  	}
  }
  int ans = 1e18;
  for(int i=0;i<H;i++){
  	ans = min(ans,dist[i*W+W-1]);
  }
  /*for(int i=0;i<H;i++){
  	for(int j=0;j<W;j++){
  		cout<<dist[i*W+j]<<' ';
  	}
  	cout<<endl;
  }*/
  cout<<(ans == 1e18 ? -1 : ans)<<endl;
}