#include <bits/stdc++.h>
using namespace std;
int n,m,mapp[110][110];
int dx[4]={1,0,0,-1};
int dy[4]={0,1,-1,0};
int ans=1,flag,maxx,minn=1e9;
struct nod{
	int x,y,t;
};
queue<nod>q;
int bfs(int x,int y){
	nod st;
	st.t=1; st.x=x; st.y=y;
	q.push(st);
	while(q.empty()==0){
		nod now=q.front(); q.pop();
		for(int i=0;i<4;i++){
			nod nxt;
			nxt.x=now.x+dx[i]; nxt.y=now.y+dy[i];
			if(nxt.x>=1&&nxt.x<=n&&nxt.y>=1&&nxt.y<=m&&mapp[nxt.x][nxt.y]<mapp[now.x][now.y]){
				nxt.t=now.t+1;
				ans=max(ans,nxt.t);
				q.push(nxt);
			}
		}
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			cin>>mapp[i][j];
			maxx=max(maxx,mapp[i][j]);
			minn=min(minn,mapp[i][j]);
		}
	}
	for(int i=n;i>=1;i--){
		for(int j=m;j>=1;j--){
			bfs(i,j);
			if(ans==maxx-minn+1){
				cout<<ans<<endl;
			    return 0;	
			} 
		}
	}
	cout<<ans<<endl;
	return 0;
}