#include<bits/stdc++.h>

using namespace std;
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<vector<int>> g(h*w);
   vector<vector<int>> gr(h*w);

   int dx[] = {1, 0, -1, 0};
   int dy[] = {0, 1, 0, -1};
   for(int i = 0;i < h;i++){
    for(int j = 0;j < w;j++){
        for(int k = 0;k < 4;k++){
            int nx = i + dx[k], ny = j + dy[k];
            if(nx < 0 || nx >= h || ny < 0 || ny >= w) continue;
            if(a[i][j] < a[nx][ny]){
                g[i*w+j].push_back(nx*w+ny);
            }
        }
    }
   }

    priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>> que;
    vector<long long> dist(h*w, 1);
    for(int i = 0;i < h*w;i++){
        que.push(make_tuple(1, a[i/w][i%w], i));
    }
    while(!que.empty()){
        auto [d, sc, v] = que.top(); que.pop();
        if(dist[v] > d) continue;
        for(auto to: g[v]){
            if(dist[to] < dist[v] + 1){
                dist[to] = dist[v] + 1;
                que.push(make_tuple(dist[to], a[to/w][to%w], to));
            }
        }
    }

    long long ans = 0;
    for(int i = 0;i < h*w;i++){
        ans = max(ans, dist[i]);
    }
    cout << ans << endl;
}