#include <iostream>
#include <queue>
#include <tuple>

using namespace std;

using pos   = tuple<long, long>;
using node  = tuple<long, long>;

const auto MAX = static_cast<long>(1e10);

int main()
{
  long m, n, x; cin >> m >> n;
  vector<vector<node>> vault(m, vector<node>(n));
  vector<vector<bool>> seen(m, vector<bool>(n, false));
  for (long i = 0; i < m; ++i) {
    for (long j = 0; j < n; ++j) {
      cin >> x; vault[i][j] = make_tuple(x, MAX);
    }
  }
  auto neighbors = [m,n](pos p) {
    long i = get<0>(p), j = get<1>(p);
    vector<pos> ns; ns.reserve(4);
    if (i >   0) ns.push_back(make_tuple(i-1,j));
    if (i < m-1) ns.push_back(make_tuple(i+1,j));
    if (j >   0) ns.push_back(make_tuple(i,j-1));
    if (j < n-1) ns.push_back(make_tuple(i,j+1));
    return ns;
  };
  auto length = [&vault](pos a, pos b) {
    auto d = get<0>(vault[get<0>(b)][get<1>(b)]) - get<0>(vault[get<0>(a)][get<1>(a)]);
    return d <= 0 ? 0 : d;
  };
  priority_queue<tuple<long, pos>> q;
  q.push(make_tuple(0, make_tuple(0, 0))); get<1>(vault[0][0]) = 0;
  while (!q.empty()) {
    auto u    = get<1>(q.top()); q.pop();
    long i    = get<0>(u), j = get<1>(u);
    auto & vu = vault[i][j];
    // cerr << "(" << get<0>(u) << "," << get<1>(u) << ") " << endl;
    if (seen[i][j]) continue;
    for (auto & v : neighbors(u)) {
      auto & vv = vault[get<0>(v)][get<1>(v)];
      auto d    = max(get<1>(vu), length(u, v));
      // cerr << "(" << get<0>(v) << "," << get<1>(v) << ") " << get<1>(vv) << " " << d << endl;
      if (d < get<1>(vv)) {
        get<1>(vv) = d; q.push(make_tuple(-d, v));
      }
    }
    seen[i][j] = true;
  }
  //  for (long i = 0; i < m; ++i) {
  //    for (long j = 0; j < n; ++j) {
  //      cerr << get<1>(vault[i][j]) << " ";
  //    }
  //    cerr << endl;
  //  }
  cout << get<1>(vault[m-1][n-1]) << endl;
}