#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;i<n;i++)
#define REP(i,a,n) for(ll i=a;i<n;i++)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define pb eb
#define be(v) (v).begin(),(v).end()
#define all(i,v) for(auto& i : v)
#define all2(i,j,v) for(auto& [i,j] : v)
template<class T, class U> void chmin(T& t, const U& u) { if (t > u) t = u; }
template<class T, class U> void chmax(T& t, const U& u) { if (t < u) t = u; }

// cin.tie(nullptr);
// ios::sync_with_stdio(false);
// cout << fixed << setprecision(20);

void solve(){
  ll h,w;
  cin >> h >> w;
  VV<ll> v(h, V<ll>(w));
  rep(i, h) rep(j, w) cin >> v[i][j];
  VV<ll> c(h, V<ll>(w, -1));
  V<set<tuple<ll,ll,ll>>> st(2);
  c[0][0] = 1;
  c[h-1][w-1] = 0;
  st[0].insert({v[h-2][w-1], h-2, w-1});
  st[0].insert({v[h-1][w-2], h-1, w-2});
  st[1].insert({v[0][1], 0, 1});
  st[1].insert({v[1][0], 1, 0});
  V<ll> dx = {0, 1, 0, -1}, dy = {1, 0, -1, 0};
  ll ans = 0;
  while(1){
    ans++;
    ll id = ans%2;
    auto[a,x,y] = *(st[ans%2].begin());
    st[ans%2].erase(st[id].begin());
    while(c[x][y]!=-1){
      auto[aa,xx,yy] = *(st[id%2].begin());
      st[id%2].erase(st[id].begin());
      x = xx;
      y = yy;
    }
    // cout << x << " " << y << endl;
    c[x][y] = id;
    ll f = 1;
    rep(i, 4){
      ll nx = x+dx[i];
      ll ny = y+dy[i];
      if(nx<0||h<=nx) continue;
      if(ny<0||w<=ny) continue;
      if(c[nx][ny]==id) continue;
      if(c[nx][ny]==1-id){
        f = 0;
        continue;
      }
      st[id].insert({v[nx][ny], nx, ny});
    }
    if(f==0) break;
  }
  cout << ans << endl;
}





int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int t=1;
  // cin >> t;
  rep(i,t) solve();
}