#include <iostream>
using namespace std;
int pmap[101][101],n,m,p,times,resn,resm;
void getnum(int n,int m,int t) //n行，m列 
{
	switch(t)
	{
		case 1: {
			resn=n-1;resm=m;
			break;
		}
		case 2: {
			resn=n;resm=m-1;
			break;
		}
		case 3: {
			resn=n+1;resm=m;
			break;
		} 
		case 4:{
			resn=n;resm=m+1;
		}
	} 
}
int gettimes(int hang,int lie)
{
	//cout<<"pos:"<<hang<<" "<<lie<<endl; 
	times++;
	int nownum=pmap[hang][lie],pmin=pmap[hang][lie],pmax=0,ph=102,pl=102,bh=102,bl=102,n;
	for(int i=1;i<5;i++)
	{
		getnum(hang,lie,i);
		int nn[]={resn,resm};
		if(nn[0]<0 || nn[1]<0) continue;
		//cout<<"t:"<<times<<" "<<nn[0]<<" "<<nn[1]<<" "<<i<<endl;
		if(pmap[nn[0]][nn[1]]>pmax && pmap[nn[0]][nn[1]]<nownum) 
		{
			pmax=pmap[nn[0]][nn[1]];
			bh=nn[0];
			bl=nn[1];
		}
		if(pmap[nn[0]][nn[1]]<pmin)
		{
			pmin=pmap[nn[0]][nn[1]];
			ph=nn[0];
			pl=nn[1];
		}
	}
	if(pmin==10001 ||(ph==102 && pl==102) ||(bh==102 && bl==102) || pmax==0) return times;
	//cout<<"re"<<endl; 
	gettimes(bh,bl);
}
int main()
{
	int tto;
	cin>>m>>n;
	for(int i=0;i<m;i++) //行 
	{
		for(int j=0;j<n;j++) 
		{ //列 
			cin>>p;
			pmap[i][j]=p; //前为行，后为列 
		}
	}
	//cout<<pmap[4][4];
	//cin>>tto;
	//getnum(0,0,tto);
	//cout<<resn<<" "<<resm<<" "<<pmap[resn][resm]<<endl;
	int nmax=0,now;
	for(int ii=0;ii<m;ii++)
	{
		//cout<<ii<<endl;
		for(int jj=0;jj<n;jj++)
		{
			times=0;
			//cout<<ii<<" "<<jj<<endl;
			//cout<<"restarted"<<endl;
			now=gettimes(ii,jj);
			if(now>nmax) nmax=now;
		}
	}
	cout<<nmax<<endl;
}