#if __INCLUDE_LEVEL__ == 0

#include __BASE_FILE__

namespace {

void solve() {
  int h, w;
  scan(h, w);
  std::vector a(h, std::vector<int>(w));
  scan(a);

  std::vector color(h, std::vector<int>(w, -1));

  std::array<std::priority_queue<std::tuple<int, int, int>>, 2> q;

  const auto push = [&](int t, int i, int j) {
    if (color[i][j] == -1) {
      q[t].emplace(-a[i][j], i, j);
    }
  };

  push(1, 0, 0);
  push(0, h - 1, w - 1);

  int ans = 0;

  for (int t = 1;;) {
    const auto [_, i, j] = q[t].top();
    q[t].pop();

    if (color[i][j] == -1) {
      color[i][j] = t;
    } else {
      continue;
    }

    ++ans;

    for (auto [ni, nj] : {std::pair{1, 0}, {0, 1}, {-1, 0}, {0, -1}}) {
      ni += i;
      nj += j;
      if (0 <= ni && ni < h && 0 <= nj && nj < w) {
        if (color[ni][nj] == (t ^ 1)) {
          print(ans - 2);
          return;
        }
        push(t, ni, nj);
      }
    }

    t ^= 1;
  }
}

}  // namespace

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout << std::setprecision(DBL_DECIMAL_DIG);

  solve();
}

#else  // __INCLUDE_LEVEL__

#include <bits/stdc++.h>

template <class T, class U = T>
bool chmin(T& x, U&& y) {
  return y < x && (x = std::forward<U>(y), true);
}

template <class T, class U = T>
bool chmax(T& x, U&& y) {
  return x < y && (x = std::forward<U>(y), true);
}

template <std::signed_integral T = int>
T inf() {
  T ret;
  std::memset(&ret, 0x3f, sizeof(ret));
  return ret;
}

template <std::floating_point T>
T inf() {
  return std::numeric_limits<T>::infinity();
}

template <class T>
concept Range = std::ranges::range<T> && !std::convertible_to<T, std::string_view>;

template <class T>
concept Tuple = std::__is_tuple_like<T>::value && !Range<T>;

namespace std {

istream& operator>>(istream& is, Range auto&& r) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

istream& operator>>(istream& is, Tuple auto&& t) {
  return apply([&](auto&... xs) -> istream& { return (is >> ... >> xs); }, t);
}

ostream& operator<<(ostream& os, Range auto&& r) {
  for (string_view sep = ""; auto&& e : r) {
    os << exchange(sep, " ") << e;
  }
  return os;
}

ostream& operator<<(ostream& os, Tuple auto&& t) {
  const auto f = [&](auto&... xs) -> ostream& {
    [[maybe_unused]] string_view sep = "";
    ((os << exchange(sep, " ") << xs), ...);
    return os;
  };
  return apply(f, t);
}

}  // namespace std

void scan(auto&&... xs) { std::cin >> std::tie(xs...); }
void print(auto&&... xs) { std::cout << std::tie(xs...) << '\n'; }

template <class F>
class fix {
 public:
  explicit fix(F f) : f_(std::move(f)) {}

  decltype(auto) operator()(auto&&... xs) const {
    return f_(std::ref(*this), std::forward<decltype(xs)>(xs)...);
  }

 private:
  F f_;
};

inline auto rep(int l, int r) { return std::views::iota(std::min(l, r), r); }
inline auto rep(int n) { return rep(0, n); }
inline auto rep1(int l, int r) { return rep(l, r + 1); }
inline auto rep1(int n) { return rep(1, n + 1); }

using namespace std::literals;

namespace ranges = std::ranges;
namespace views = std::views;

using i64 = std::int64_t;

#endif  // __INCLUDE_LEVEL__