#include <bits/stdc++.h>
using namespace std;
const long long INF = 1e18;
const int N = 1005;
const int dx[] = {0, 0, -1, +1}, dy[] = {-1, +1, 0, 0};
int n, m;
int a[N][N];
long long dp[N][N];
long long res = -INF;
vector < pair<int,int> > vals;
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
cin >> a[i][j];
}
}
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
for (int k = 1; k <= n; ++k) {
for (int l = 1; l <= m; ++l) {
int diff = abs(i - k) + abs(j - l) + 1;
res = max(res, (long long)a[i][j] - a[k][l] - diff);
}
}
}
}
cout << res << endl;
}
