#include <iostream>
#include <algorithm>
using namespace std;

#define NUM 120
struct node{
	int x;
	int y;
	int num;
}N[NUM*NUM];
int M[NUM][NUM];
int P[NUM][NUM];

bool cmp(const node & a,const node &b){
	return a.num>b.num;
}

int main()
{
	int ans=1;
	int h,w,temp;
	cin>>h>>w;
	int i,j,n;
	for (i=0;i<h;i++) for (j=0;j<w;j++){
		cin>>n;M[i][j]=n;
		N[i*w+j].x=i;N[i*w+j].y=j;N[i*w+j].num=n;
	}
	sort(N,N+h*w,cmp);
	for (i=0;i<h*w;i++){
		temp=1;
		if (N[i].y>0 && M[N[i].x][N[i].y-1]>N[i].num && P[N[i].x][N[i].y-1]+1>temp)
			temp = P[N[i].x][N[i].y-1]+1;

		if (N[i].y<w && M[N[i].x][N[i].y+1]>N[i].num && P[N[i].x][N[i].y+1]+1>temp)
			temp = P[N[i].x][N[i].y+1]+1;
		
		if (N[i].x>0 && M[N[i].x-1][N[i].y]>N[i].num && P[N[i].x-1][N[i].y]+1>temp)
			temp = P[N[i].x-1][N[i].y]+1;


		if (N[i].x<h && M[N[i].x+1][N[i].y]>N[i].num && P[N[i].x+1][N[i].y]+1>temp)
			temp = P[N[i].x+1][N[i].y]+1;
		P[N[i].x][N[i].y]=temp;
		if (temp>ans) ans=temp;
	}
	cout<<ans<<endl;
	return 0;
}