#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<int> order(h * w);
  iota(begin(order), end(order), 0);
  ranges::sort(order, {}, [&](const int i) -> int { return a[i / w][i % w]; });
  vector dp(h, vector(w, 1));
  for (const int id : order) {
    const int y = id / w, x = id % w;
    REP(d, 4) {
      const int ny = y + DY4[d], nx = x + DX4[d];
      if (0 <= ny && ny < h && 0 <= nx && nx < w && a[y][x] < a[ny][nx]) {
        chmax(dp[ny][nx], dp[y][x] + 1);
      }
    }
  }
  int ans = 0;
  for (const vector<int>& dp_i : dp) chmax(ans, ranges::max(dp_i));
  cout << ans << '\n';
  return 0;
}