// #pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
// #include <x86intrin.h>
using namespace std;
#if __cplusplus >= 202002L
using namespace numbers;
#endif



int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	static const vector<pair<int, int>> dr4{{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
	int h, w;
	cin >> h >> w;
	vector<vector<int>> a(h, vector<int>(w));
	for(auto &x: a | ranges::views::join){
		cin >> x;
	}
	vector<array<int, 2>> order;
	for(auto i = 0; i < h; ++ i){
		for(auto j = 0; j < w; ++ j){
			order.push_back({i, j});
		}
	}
	ranges::sort(order, [&](auto x, auto y){ return a[x[0]][x[1]] < a[y[0]][y[1]]; });
	vector<vector<int>> dp(h, vector<int>(w, 1));
	for(auto [x, y]: order){
		for(auto [dx, dy]: dr4){
			int xn = x + dx, yn = y + dy;
			if(0 <= min(xn, yn) && xn < h && yn < w && a[x][y] < a[xn][yn]){
				dp[xn][yn] = max(dp[xn][yn], dp[x][y] + 1);
			}
		}
	}
	cout << ranges::max(dp | ranges::views::join) << "\n";
	return 0;
}

/*

*/