#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e9+7;
const ll MOD = 998244353;
typedef pair<ll,ll> ii;
#define iii pair<ii,ll>
#define f(i,a,b) for(ll i = a;i < b;i++)
#define pb push_back
#define vll vector<ll>
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
///I hope I will get uprating and don't make mistakes
///I will never stop programming
///sqrt(-1) Love C++
///Please don't hack me
///@TheofanisOrfanou Theo830
///Think different approaches (bs,dp,greedy,graphs,shortest paths,mst)
///Stay Calm
///Look for special cases
///Beware of overflow and array bounds
///Think the problem backwards
///Training
int main(void){
ll n,m;
cin>>n>>m;
ll ans = -1e18;
ll arr[n][m];
f(i,0,n){
f(j,0,m){
cin>>arr[i][j];
}
}
f(i,0,n){
f(j,0,m){
f(ii,0,n){
f(jj,0,m){
ans = max(ans,arr[i][j] - arr[ii][jj] - abs(ii-i) - abs(jj-j) - 1);
}
}
}
}
cout<<ans<<"\n";
}
