#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

vector<int> topological_sort (vector<vector<int>>& graph) {
    vector<int> res(0);
    vector<bool> vis(graph.size(), false);

    auto dfs = [&](auto self, int pos) -> void {
        vis[pos] = true;
        for (auto to: graph[pos]) {
            if (vis[to]) continue;
            self(self, to);
        }

        res.push_back(pos);
    };

    for (int i = 0; i < graph.size(); i++) if (!vis[i]) dfs(dfs, i);
    reverse(res.begin(), res.end());

    return res;
}

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];
        }
    }

    const int dxy[][2] = {
        {1, 0},
        {-1, 0},
        {0, 1},
        {0, -1},
    };

    auto is_in = [&](int y, int x) {
        return 0 <= y && y < H && 0 <= x && x < W;
    };

    vector<vector<int>> graph(H * W);

    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
            for (auto d: dxy) {
                int ni = i + d[0], nj = j + d[1];
                if (!is_in(ni, nj)) continue;

                if (A[i][j] < A[ni][nj]) {
                    graph[i * W + j].push_back(ni * W + nj);
                }
            }
        }
    }

    auto update_ord = topological_sort(graph);

    vector<int> score(H * W, 1);
    for (auto v: update_ord) {
        for (auto nex: graph[v]) {
            score[nex] = max(score[nex], score[v] + 1);
        }
    }

    int ans = 0;
    for (auto v: score) ans = max(ans, v);

    cout << ans << "\n";
}