#include "bits/stdc++.h"
using namespace std;
#define int long long
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ss second
#define ff first
#define pb push_back
void solve(){
int n, m; cin >> n >> m;
vector<vector<int>> grid(n, vector<int> (m));
vector<pair<int, int>> vp;
int mx = 0;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
cin >> grid[i][j];
}
}
int ans = -1;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
for(int ii = i; ii < n; ii ++){
for(int jj = j + 1; jj < m; jj++){
ans = max(ans, abs(grid[i][j] - grid[ii][jj]) - (abs(i - ii) + abs(j - jj) + 1));
}
}
}
}
cout << ans;
}
signed main() {
cin.tie(nullptr)->sync_with_stdio(false);
int t = 1; //cin >> t;
while(t--){
solve();
//cout << endl;
}
return 0;
}
