#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using Matrix = vector<vector<ll>>;
const int inf = 1000000000;
const ll INF = 1000000000000000000;
const ll mod = 998244353;
const ull mod_hash = (1UL << 61) - 1;
const vector<int> dx = {0, 1, 0, -1, 1, 1, -1, -1};
const vector<int> dy = {1, 0, -1, 0, 1, -1, 1, -1};

int main(){
  int H,W;cin>>H>>W;
  vector<vector<ll>> G(H,vector<ll>(W));
  for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) cin>>G[i][j];
  set<ll> seen;
  set<pair<ll,ll>> zero, one;
  one.insert({G[0][1], 1});
  one.insert({G[1][0], W});
  zero.insert({G[H-1][W-2], (H-1)*W + W - 2});
  zero.insert({G[H-2][W-1], (H-2)*W + W - 1});
  seen.insert(0);
  seen.insert((H - 1) * W + W - 1);
  int turn = 1;
  int ans = 0;
  while(true){
    pair<ll,ll> ne;
    if(turn&1){
      ne = *one.begin();
      one.erase(one.begin());
    }else{
      ne = *zero.begin();
      zero.erase(zero.begin());
    }
    ans++;
    if(turn&1){
      if(zero.count(ne))break;
    }else{
      if(one.count(ne))break;
    }
    seen.insert(ne.second);
    int x = ne.second/W;
    int y = ne.second%W;
    for (int d = 0; d < 4; d++) {
      int xx = x + dx[d];
      int yy = y + dy[d];
      if(xx< 0 || xx >= H || yy < 0 || yy >= W)continue;
      if(seen.count(xx*W+yy))continue;
      if(turn&1){
        one.insert({G[xx][yy], xx*W+yy});
      }else{
        zero.insert({G[xx][yy], xx*W+yy});
      }
    }
    turn ^= 1;
  }
  cout << ans << endl;
  return 0;
}