#include<bits/stdc++.h>
using namespace std;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N,M;
  cin>>N>>M;
  vector<vector<int>>A(N,vector<int>(M));
  for(int i=0;i<N;i++){
    for(int j=0;j<M;j++)cin>>A[i][j];
  }
  vector<vector<array<long long,2>>>dist(N,vector<array<long long,2>>(M,{(long long)1e18,(long long)1e18}));
  priority_queue<array<long long,4>,vector<array<long long,4>>,greater<array<long long,4>>>pq;
  pq.push({0,0,0,0});
  dist[0][0][0]=0;
  while(pq.size()){
    long long d=pq.top()[0],f=pq.top()[1],r=pq.top()[2],e=pq.top()[3];
    pq.pop();
    if(dist[f][r][e]<d)continue;
    if(e==0){
      if(r>0&&dist[f][r-1][0]>d){
        dist[f][r-1][0]=d;
        pq.push({d,f,r-1,0});
      }
      if(r+1<M&&dist[f][r+1][0]>d){
        dist[f][r+1][0]=d;
        pq.push({d,f,r+1,0});
      }
      if(dist[f][r][1]>d+A[f][r]){
        dist[f][r][1]=d+A[f][r];
        pq.push({d+A[f][r],f,r,1});
      }
    }else{
      if(dist[f][r][0]>d){
        dist[f][r][0]=d;
        pq.push({d,f,r,0});
      }
      if(f+1<N&&dist[f+1][r][1]>d+A[f+1][r]){
        dist[f+1][r][1]=d+A[f+1][r];
        pq.push({d+A[f+1][r],f+1,r,1});
      }
    }
  }
  long long ans=1e18;
  for(int i=0;i<M;i++)ans=min(ans,dist[N-1][i][0]);
  cout<<ans<<'\n';
}