#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int H,W; cin >> H >> W;
    vector<tuple<int,int,int>> X;
    vector<vector<int>> A(H,vector<int>(W));
    for(int i=0; i<H; i++) for(int k=0; k<W; k++){
        int a; cin >> a;
        A.at(i).at(k) = a;
        X.push_back({a,i,k});
    }
    sort(X.rbegin(),X.rend());

    vector dist(H,vector<int>(W));
    vector<int> dx = {-1,0,1,0},dy = {0,1,0,-1};
    for(auto [a,x,y] : X){
        int now = dist.at(x).at(y);
        for(int i=0; i<4; i++){
            int nx = x+dx.at(i),ny = y+dy.at(i);
            if(nx < 0 || nx >= H || ny < 0 || ny >= W) continue;
            if(A.at(nx).at(ny) >= a) continue;
            dist.at(nx).at(ny) = max(dist.at(nx).at(ny),now+1);
        }
    }


    int answer = 0;
    for(auto &h : dist) for(auto &w : h) answer = max(answer,w);
    cout << answer+1 << endl; 
}