#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
	int h, w;
	cin >> h >> w;
	vector<vector<int>> a(h, vector<int>(w));
	vector<pair<int, pair<int, int>>> vs;
	rep(i,h)rep(j,w){
		cin >> a[i][j];
		vs.emplace_back(a[i][j], make_pair(i, j));
	}
	sort(vs.begin(),vs.end());
	vector<int> di = {0,1,0,-1};
	vector<int> dj = {1,0,-1,0};
	vector<vector<int>> dp(h, vector<int>(w,1));
	for(auto [val, pos] : vs) {
		auto [x, y] = pos;
		rep(d,4){
			int nx = x + di[d];
			int ny = y + dj[d];
			if(nx<0 || ny<0 || nx>=h || ny>=w || a[nx][ny]<=val) continue;
			dp[nx][ny] = max(dp[nx][ny], dp[x][y]+1);
		}
	}
	int ans = 0;
	rep(i,h)rep(j,w) ans = max(ans, dp[i][j]);
	cout << ans << endl;
	return 0;
}