#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

int dx[4] = {-1, 0, 0, 1};
int dy[4] = {0, -1, 1, 0};

int main() {
  int h, w; cin >> h >> w;
  vector<vector<int>> a(h, vector<int>(w));
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) cin >> a[i][j];
  }
  vector<int> ord(h * w);
  for (int i = 0; i < h * w; i++) ord[i] = i;
  sort(ord.begin(), ord.end(), [&](int l, int r) {
    return a[l / w][l % w] < a[r / w][r % w];
  });
  vector<vector<int>> dp(h, vector<int>(w));
  for (int i = 0; i < h * w; i++) {
    int x = ord[i] / w;
    int y = ord[i] % w;
    dp[x][y] = 1;
    for (int j = 0; j < 4; j++) {
      int nx = x + dx[j];
      int ny = y + dy[j];
      if (0 > nx || nx >= h || 0 > ny || ny >= w) continue;
      if (a[nx][ny] < a[x][y]) {
        dp[x][y] = max(dp[x][y], dp[nx][ny] + 1);
      }
    }
  }
  int ans = 0;
  for (int i = 0; i < h * w; i++) ans = max(ans, dp[i / w][i % w]);
  cout << ans << endl;
  return 0;
}