#include<iostream>
#include<stdlib.h>
using namespace std;
int m,n;
int a[110][110];
int c[110][110];
struct point
{
  int value;
  int x;
  int y;
};
int fun(int i,int j)
{
   int sum1=0,sum2=0,sum3=0,sum4=0;
   int max1,max2,max; 
   if(a[i][j]<=a[i-1][j]&&a[i][j]<=a[i+1][j]&&a[i][j]<=a[i][j-1]&&a[i][j]<=a[i][j+1])
	   return 1;
   if(i>1&&a[i][j]>a[i-1][j])
   {
	   if(c[i-1][j]==-1)
          c[i-1][j]=fun(i-1,j);
   }
	if(i<m&&a[i][j]>a[i+1][j])
	{
		if(c[i+1][j]==-1)
		c[i+1][j]=fun(i+1,j);}
	if(j>1&&a[i][j]>a[i][j-1])
	{
	   if(c[i][j-1]==-1)
		c[i][j-1]=fun(i,j-1);
	}
	if(j<n&&a[i][j]>a[i][j+1]){
        if(c[i][j+1]==-1)
		c[i][j+1]=fun(i,j+1);}
    if(c[i-1][j]>c[i+1][j])
		max1=c[i-1][j];
	else
		max1=c[i+1][j];
	if(c[i][j-1]>c[i][j+1])
		max2=c[i][j-1];
	else
		max2=c[i][j+1];
	if(max1>max2)
		max=max1;
	else
		max=max2;
	return max+1;
}
int main()
{
   
   cin>>m>>n;
   
      int i,j;
	  memset(c,-1,sizeof(c));
	  if(m==0||n==0)
	  {cout<<"1"<<endl;
	   
	  }
	  else{
	  point b[11000];
	  int l=0;
	  for(i=0;i<=m+1;i++)
	  {a[0][i]=1100000000;
	    a[m+1][i]=1100000000;
	  }
	  for(i=0;i<=n+1;i++)
	  {
	     a[i][0]=1100000000;
		 a[i][n+1]=1100000000;
	  }
	  for(i=1;i<=m;i++)
		  for(j=1;j<=n;j++)
		  {cin>>a[i][j];
		  
		  
		  }
	
		  for(i=1;i<=m;i++)
			  for(j=1;j<=n;j++)
			  {if(a[i][j]==-1)
			     continue;
				  b[l].value=fun(i,j);
			  b[l].x=i;
			  b[l].y=j;
			  l++;
			  memset(c,-1,sizeof(c));
			 
			  }
			
			  int flag=0;
			  for(i=0;i<l;i++)
			  {if(b[flag].value<b[i].value)
					  flag=i;
			 
			  }
		
				  cout<<b[flag].value<<endl;
	  }
   return 0;
}