/*
Let the good times roll
*/
#include <iostream>
#include <cstdio>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>
#include <cstring>
#include <cfloat>
#include <cmath>
#include <cassert>
#include <locale>
#include <string>
#include <bitset>
#include <functional>
#include <climits>
#include <iomanip>
using namespace std;
#define read(x) freopen(x,"r",stdin)
#define write(x) freopen(x,"w",stdout)
#define cl(a,b) memset(a,b,sizeof(a))
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ll long long
#define ld long double
#define vec vector
#define vi vec<int>
#define heap priority_queue
#define res reserve
#define pb push_back
#define f(x,y,z) for(int x=(y); x<(z); x++)
#define fd(x,y,z) for(int x=(y); x>=(z); x--)
#define fit(x,y) for(auto x: y)
#define srt(x) sort(all(x))
#define rsrt(x) sort(rall(x))
#define make_unique(x) sort(all((x))); (x).resize(unique(all((x))) - (x).begin())
#define pii pair<int,ll>
#define ppi pair<pii,int>
#define pip pair<int,pii>
#define mp make_pair
#define f1 first
#define s2 second
#define cdbg(x) cerr<<#x<<" = "<<x<<",\t";
#define cdbl cerr<<"\n----------\n";
#define pow2(x) ((x)*(x))
#define edist(x1, y1, x2, y2) (sqrt((pow2(x1-x2)+pow2(y1-y2))))
#define mdist(x1, y1, x2, y2) (abs((x1)-(x2))+abs((y1)-(y2)))
#define y1 FullSensei
#define mid ((ss+se)>>1)
#define left (si<<1)
#define right ((si<<1)+1)
#define pi 3.141592653589793
#define popcount __builtin_popcount
#define spc ' '
#define endl '\n'
bool checkbit(int x,int y){return (x&(1<<y));}
int setbit(int x,int y){return (x^(1<<y));}
const int dirs[4][2]={{1,0},{0,1},{-1,0},{0,-1}};
const int mod=1e9+7;
const int p1=805306457;
const int p2=1610612741;
const int INF=1e9;
const int N=50+7;
int a[N][N];
int n, m;
int main(){
//read("in.in");
cin>>n>>m;
f(i,1,n+1){
f(j,1,m+1){
cin>>a[i][j];
}
}
ll ans=-1;
f(i1,1,n+1){
f(j1,1,m+1){
f(i2,1,n+1){
f(j2,1,m+1){
ll weight=abs(a[i1][j1]-a[i2][j2])-(abs(i1-i2)+abs(j1-j2)+1);
/*if(ans<weight){
cerr<<i1<<spc<<j1<<spc<<i2<<spc<<j2<<spc<<"weight: "<<weight<<endl;
}*/
ans=max(ans,weight);
}
}
}
}
cout<<ans<<endl;
return 0;
}
