#include <atcoder/all>
#include <bits/stdc++.h>
using ll = long long;
using ull = unsigned long long;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
using namespace std;
using namespace atcoder;
using mint = modint998244353;
const int inf = 1000000007;
const ll longinf = 1ll << 60;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int h, w;
    cin >> h >> w;
    vector<vector<int>> a(h, vector<int>(w, 0));
    rep(i, h) rep(j, w) cin >> a[i][j];
    vector<pair<int, int>> ord;
    rep(i, h) rep(j, w) ord.push_back({i, j});
    sort(ord.begin(), ord.end(), [&](pair<int, int> x, pair<int, int> y) {
        return a[x.first][x.second] < a[y.first][y.second];
    });
    vector dp(h, vector<int>(w, 1));
    vector<int> d = {1, 0, -1, 0, 1};
    int ans = 0;
    for(auto [x, y] : ord) {
        rep(i, 4) {
            int nx = x + d[i], ny = y + d[i + 1];
            if(0 <= nx && nx < h && 0 <= ny && ny < w && a[nx][ny] < a[x][y]) {
                dp[x][y] = max(dp[nx][ny] + 1, dp[x][y]);
            }
        }
        ans = max(ans, dp[x][y]);
    }
    cout << ans << endl;
    return 0;
}