#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
const int di[] = {1, 0, -1, 0};
const int dj[] = {0, 1, 0, -1};

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w;
  cin >> h >> w;
  VVI a(h, VI(w));
  rep(i, h) rep(j, w) cin >> a[i][j];
  vector<P> ord(h * w);
  rep(i, h) rep(j, w) ord[i * w + j] = {i, j};
  sort(ord.begin(), ord.end(), [&](P i, P j) {
    return a[i.first][i.second] < a[j.first][j.second];
  });
  VVI dp(h, VI(w, 1));
  auto idxchk = [&](int i, int j) { return 0 <= i && i < h && 0 <= j && j < w; };
  int ans = 0;
  for (auto [i, j] : ord) {
    rep(k, 4) {
      int ni = i + di[k], nj = j + dj[k];
      if (!idxchk(ni, nj) || a[ni][nj] >= a[i][j]) continue;
      chmax(dp[i][j], dp[ni][nj] + 1);
    }
    chmax(ans, dp[i][j]);
  }
  cout << ans << '\n';
}