#include <iostream>
#include <vector>
#include <queue>

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];

    // DAGになるやつ -> 最長経路問題はdpで求まる
    auto is_in = [&](int i, int j) {
        return 0 <= i && i < H && 0 <= j && j < W;
    };

    vector<vector<int>> indeg(H, vector<int>(W));

    const vector<pair<int, int>> dxy = {
        make_pair(0, 1),
        make_pair(1, 0),
        make_pair(0, -1),
        make_pair(-1, 0),
    };

    for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) {
        for (auto& d : dxy) {
            int y = i + d.first;
            int x = j + d.second;

            if (!is_in(y, x)) continue;
            if (A[i][j] < A[y][x]) indeg[y][x]++;
        }
    }

    vector<vector<int>> vis(H, vector<int>(W, -1));
    queue<pair<int, int>> Q;

    for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) {
        if (indeg[i][j] == 0) Q.push(make_pair(i, j));
    }

    while (!Q.empty()) {
        auto pos = Q.front(); Q.pop();
        int i = pos.first;
        int j = pos.second;
        if (vis[i][j] == -1) vis[i][j] = 0;

        for (auto& d : dxy) {
            int y = i + d.first;
            int x = j + d.second;
            if (!is_in(y, x)) continue;
            if (A[y][x] <= A[i][j]) continue;

            vis[y][x] = max(vis[y][x], vis[i][j] + 1);

            indeg[y][x]--;
            if (indeg[y][x] == 0) Q.push(make_pair(y, x));
        }
    }

    int ans = 0;
    for (int i = 0; i < H; i++) for (int j = 0; j < W; j++) ans = max(ans, vis[i][j] + 1);

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