#include <bits/stdc++.h>
using namespace std;
vector<int> dx = {1, 0, -1, 0};
vector<int> dy = {0, 1, 0, -1};
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<pair<int, int>> P(H * W);
  for (int i = 0; i < H * W; i++){
    P[i] = make_pair(i / W, i % W);
  }
  sort(P.begin(), P.end(), [&](pair<int, int> a, pair<int, int> b){
    return A[a.first][a.second] < A[b.first][b.second];
  });
  vector<vector<int>> dp(H, vector<int>(W, 1));
  int ans = 1;
  for (int i = 0; i < H * W; i++){
    int x = P[i].first;
    int y = P[i].second;
    for (int j = 0; j < 4; j++){
      int x2 = x + dx[j];
      int y2 = y + dy[j];
      if (0 <= x2 && x2 < H && 0 <= y2 && y2 < W){
        if (A[x2][y2] < A[x][y]){
          dp[x][y] = max(dp[x][y], dp[x2][y2] + 1);
          ans = max(ans, dp[x][y]);
        }
      }
    }
  }
  cout << ans << endl;
}