#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int h, w; cin >> h >> w;
  vector a(h, vector(w, 0));
  for (vector<int>& a_i : a) for (int& a_ij : a_i) cin >> a_ij;
  vector color(h, vector(w, -1));
  color[0][0] = 1;
  color[h - 1][w - 1] = 0;
  array<priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>, greater<tuple<int, int, int>>>, 2> que{};
  que[0].emplace(a[h - 1][w - 2], h - 1, w - 2);
  que[0].emplace(a[h - 2][w - 1], h - 2, w - 1);
  que[1].emplace(a[0][1], 0, 1);
  que[1].emplace(a[1][0], 1, 0);
  for (int ans = 1; ; ++ans) {
    int y = -1, x = -1;
    while (true) {
      tie(ignore, y, x) = que[ans % 2].top();
      que[ans % 2].pop();
      if (color[y][x] == -1) break;
    }
    color[y][x] = ans % 2;
    REP(k, 4) {
      const int ny = y + DY4[k], nx = x + DX4[k];
      if (0 <= ny && ny < h && 0 <= nx && nx < w) {
        if (color[ny][nx] == -1) {
          que[ans % 2].emplace(a[ny][nx], ny, nx);
        } else if (color[ny][nx] != color[y][x]) {
          cout << ans << '\n';
          return 0;
        }
      }
    }
  }
}