#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

const int dx[4] = { 1,0,-1,0 };
const int dy[4] = { 0,-1,0,1 };
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w; cin >> h >> w;
	vector a(h, vector<int>(w));
	vector dp(h, vector<int>(w, 1));
	vector<pair<int, P>>v;
	rep(i, h)rep(j, w) {
		cin >> a[i][j];
		v.push_back({ a[i][j],{i,j} });
	}
	sort(all(v));
	rep(i, v.size()) {
		int x = v[i].second.first;
		int y = v[i].second.second;
		int val = v[i].first;
		rep(t, 4) {
			int nx = x + dx[t];
			int ny = y + dy[t];
			if (nx < 0 || nx >= h)continue;
			if (ny < 0 || ny >= w)continue;
			if (val <= a[nx][ny])continue;
			chmax(dp[x][y], dp[nx][ny] + 1);
		}
	}
	int ans = 0;
	rep(i, h)rep(j, w)chmax(ans, dp[i][j]);
	cout << ans << endl;
	return 0;
}