#include <iostream>
#include <vector>

using namespace std;

constexpr int DX[] = {0, 1, 0, -1};
constexpr int DY[] = {1, 0, -1, 0};

int path_length = 0;

void log_grid(const vector<vector<int>>& grid, string name) {
    for (const auto& row : grid) {
        clog << name << ": ";
        for (const auto& cell : row) {
            clog << cell << " ";
        }
        clog << endl;
    }
}

int dfs(const vector<vector<int>>& grid, const int x, const int y,
        vector<vector<int>>& calculated_depths, const int _depth = 1) {
    const unsigned int r = grid.size(), c = grid[0].size();

    const int current_num = grid[x][y];
    if (calculated_depths[x][y] > 0) { return calculated_depths[x][y] + _depth - 1; }

    if (_depth + current_num <= path_length) {
        // clog << "CUT " << x << "," << y << ":" << current_num << ", " << _depth << endl;
        return -1;
    } // 剪枝
    // if (current_num == 1) { return _depth; }
    // clog << x << "," << y << ":" << current_num << ", " << _depth << endl;

    int best_depth = _depth;

    for (int i = 0; i < 4; i++) {
        const int nx = x + DX[i], ny = y + DY[i];
        if (nx >= 0 && nx < r && ny >= 0 && ny < c && grid[nx][ny] < current_num) {
            int next_depth = dfs(grid, nx, ny, calculated_depths, _depth + 1);
            best_depth = max(best_depth, next_depth);
        }
    }
    path_length = max(path_length, best_depth);
    calculated_depths[x][y] = best_depth - _depth + 1;
    return best_depth;
}


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

    int r, c;
    cin >> r >> c;

    vector<vector<int>> grid(r, vector<int>(c));
    vector<vector<int>> calculated_depths(r, vector<int>(c, 0));

    for (int i = 0; i < r; i++) {
        for (int j = 0; j < c; j++) {
            cin >> grid[i][j];
        }
    }
    for (int i = 0; i < r; i++) {
        for (int j = 0; j < c; j++) {
            dfs(grid, i, j, calculated_depths);
            // clog << "---" << endl;
            // log_grid(calculated_depths, "calculated_depths");
            // clog << "---" << endl;
        }
    }
    cout << path_length << endl;

    return 0;
}