//#pragma GCC optimize("O3")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native")
//#pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int mod = 1e9 + 7;
const int N = 1e3;
int a[N * N];
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int ans = -1;
int n, m;
cin >> n >> m;
for (int i = 0; i < n * m; i++) {
cin >> a[i];
}
for (int i = 0; i < n * m; i++) {
for (int j = 0; j < n * m; j++) {
int x1 = i / m, y1 = i % m;
int x2 = j / m, y2 = j % m;
ans = max(ans, max(a[i], a[j]) - min(a[i], a[j]) - abs(x1 - x2) - abs(y1 - y2) - 1);
}
}
cout << ans;
return 0;
}
