#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001


int main(){
	
	int H,W;
	cin>>H>>W;
	vector a(H,vector<int>(W,-1));
	rep(i,H){
		if(i==0||i==H-1)continue;
		rep(j,W){
			cin>>a[i][j];
		}
	}
	rep(i,H){
		a[i].insert(a[i].begin(),0);
		a[i].push_back(0);
	}
	vector dis(H,vector<long long>(W+2,Inf64));
	priority_queue<pair<long long,pair<int,int>>,vector<pair<long long,pair<int,int>>>,greater<pair<long long,pair<int,int>>>> Q;
	rep(i,H){
		dis[i][0] = 0;
		Q.emplace(0,make_pair(i,0));
	}
	while(Q.size()>0){
		long long D = Q.top().first;
		int x = Q.top().second.first;
		int y = Q.top().second.second;
		Q.pop();
		if(dis[x][y]!=D)continue;
		for(int i=-1;i<=1;i++){
			for(int j=-1;j<=1;j++){
				int xx = x+i,yy = y+j;
				if(xx<0||xx>=H||yy<0||yy>=W+2)continue;
				//cout<<xx<<','<<yy<<endl;
				if(a[xx][yy] == -1)continue;
				long long nD = D + a[xx][yy];
				if(dis[xx][yy]>nD){
					dis[xx][yy] = nD;
					Q.emplace(nD,make_pair(xx,yy));
				}
			}
		}
	}
	/*rep(i,H){
		rep(j,W+2){
		cout<<dis[i][j]<<',';
		}
		cout<<endl;
	}
	*/
	long long ans = dis[0].back();
	if(ans==Inf64)ans = -1;
	cout<<ans<<endl;
	
	return 0;
}