/*#pragma GCC optimize("O3")
#pragma GCC target ("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")*/
#include <bits/stdc++.h>
#pragma GCC optimize ("unroll-loops,Ofast,O3")
#pragma GCC target("avx,avx2,fma")
//#define file(data) freopen(data".in", "r", stdin); freopen(data".out", "w", stdout);
#define pb push_back
//#define ios ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define all(data) data.begin() , data.end()
#define endl '\n'
//freopen("nenokku_easy.in", "r", stdin);
//freopen("nenokku_easy.out", "w", stdout);
//#define int long long
#define pii pair < int, int >
//#define pll pair < long long, long long >
using namespace std;
const int N = 1e3 + 5;
const int lg = 21;
int n, m, c[N][N];
main() {
//file("pieaters");
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
vector < pair < int, pii > > v;
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= m; j++) {
cin >> c[i][j];
v.pb({c[i][j], {i, j}});
}
}
sort(all(v));
int ans = -1;
for(int i = v.size() - 1; i > 0; i--) {
for(int j = i - 1; j >= 0; j--) {
ans = max(ans, v[i].first - v[j].first - abs(v[i].second.first - v[j].second.first) - abs(v[i].second.second - v[j].second.second) - 1);
}
}
cout << ans;
}
