#include <iostream>
using namespace std;
const int N = 310;

int g[N][N], dp[N][N], ans;
int n, m;

void bfs(int x, int y){
	if (dp[x][y])	return;
	int dx[4] = {0, 0, 1, -1}, dy[4] = {1, -1, 0, 0};
	for (int i = 0; i < 4; i++){
		int a = x + dx[i], b = y + dy[i];
		if (a > 0 && a <= n && b > 0 && b <= m && g[a][b] < g[x][y]){
			if (!dp[a][b])	bfs(a, b);
			dp[x][y] = max(dp[x][y] ,dp[a][b]);
		}
	}
	dp[x][y]++;
	ans = max(ans, dp[x][y]);
}

int main(){
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			scanf("%d", &g[i][j]);
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			bfs(i, j);
	printf("%d", ans);
}