#include "bits/stdc++.h"
using namespace std;
#define SZ(s) (int)s.size()
#define ff first
#define ss second
#define ll long long
const int N = 1e3 + 5;
const int M = 998244353;
ll T, n, m, a[N][N];
signed main(){
ios::sync_with_stdio(false); cin.tie(nullptr);
cin >> n >> m;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= m; j++){
cin >> a[i][j];
}
}
ll ans = 0;
for(int i1 = 1; i1 <= n; i1++){
for(int j1 = 1; j1 <= m; j1++){
for(int i2 = 1; i2 <= n; i2++){
for(int j2 = 1; j2 <= m; j2++){
ans = max(ans, abs(a[i2][j2] - a[i1][j1]) - abs(i1-i2) - abs(j1-j2) - 1);
}
}
}
}
cout << ans << '\n';
return 0;
}
