#include<bits/stdc++.h>
using namespace std;
using ll=long long;
constexpr int MOD=998244353;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int H,W;
  cin>>H>>W;
  vector A(H,vector(W,0));
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      cin>>A[i][j];
    }
  }
  vector used0(H,vector(W,false)),used1=used0;
  vector colored(H,vector(W,0));
  using a3i=array<int,3>;
  priority_queue<a3i,vector<a3i>,greater<a3i>>pq0,pq1;
  pq0.push({0,0,0});
  used0[0][0]=1;
  pq1.push({0,H-1,W-1});
  used1[H-1][W-1]=1;
  int ans=-2;
  int dx[]={0,1,0,-1};
  int dy[]={-1,0,1,0};
  auto bound_ok=[&](int x,int y){
    return x>=0&&x<H &&y>=0&&y<W;
  };
  while(1){
    {
      while(pq0.size()&&colored[pq0.top()[1]][pq0.top()[2]]){
        pq0.pop();
      }
      if(pq0.empty())break;
      auto [d,i,j]=pq0.top();
      colored[i][j]=1;
      ans+=1;
      pq0.pop();
      bool ng=0;
      for(int k=0;k<4;k++){
        int i2=i+dx[k],j2=j+dy[k];
        if(bound_ok(i2,j2)&&colored[i2][j2]==2){
          ng=1;
          break;
        }else if(bound_ok(i2,j2)&&!used0[i2][j2]){
          used0[i2][j2]=1;
          pq0.push({A[i2][j2],i2,j2});
        }
      }
      if(ng)break;
    }
    {
      while(pq1.size()&&colored[pq1.top()[1]][pq1.top()[2]]){
        pq1.pop();
      }
      if(pq1.empty())break;
      auto [d,i,j]=pq1.top();
      colored[i][j]=2;
      ans+=1;
      pq1.pop();
      bool ng=0;
      for(int k=0;k<4;k++){
        int i2=i+dx[k],j2=j+dy[k];
        if(bound_ok(i2,j2)&&colored[i2][j2]==1){
          ng=1;
          break;
        }else if(bound_ok(i2,j2)&&!used1[i2][j2]){
          used1[i2][j2]=1;
          pq1.push({A[i2][j2],i2,j2});
        }
      }
      if(ng)break;
    }
  }
  cout<<ans<<'\n';
}