#include <bits/stdc++.h>
#ifdef LOCAL
#include "./debug.cpp"
#else
#define debug(...)
#define print_line
#endif
using namespace std;
using ll = long long;

const vector<int> dx = {0, 1, 0, -1};
const vector<int> dy = {1, 0, -1, 0};

int main() {
    int H, W;
    cin >> H >> W;
    vector<tuple<int, int, int>> P;
    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], P.push_back(make_tuple(A[i][j], i, j));
    sort(P.rbegin(), P.rend());

    int ans = 0;
    vector<vector<int>> dp(H, vector<int>(W, 0));
    for (auto [a, i, j] : P) {
        int res = 0;
        for (int d = 0; d < 4; d++) {
            int ni = i + dx[d], nj = j + dy[d];
            if (0 <= ni && ni < H && 0 <= nj && nj < W && A[ni][nj] > A[i][j]) res = max(res, dp[ni][nj] + 1);
        }
        dp[i][j] = res;
        ans = max(ans, res);
    }

    cout << ++ans << endl;
}