#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
#pragma GCC optimize("Ofast")
#pragma GCC target("tune=native")
#pragma GCC optimize("unroll-loops")
typedef long long ll;
typedef long double ld;
#define fs first
#define sc second
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define maxn 200000
#define BIG 1000000000000000000
mt19937 rnd(42);
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<vector<int> > a(n, vector<int>(m));
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++)
cin >> a[i][j];
}
ll time = 0;
int ans = -1e9;
auto st = steady_clock().now();
while(1){
int x = rnd(); x = abs(x); x %= n;
int y = rnd(); y = abs(y); y %= m;
int p1 = a[x][y];
// cout << x << " " << y << "\n";
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++){
int p2 = a[i][j];
ans = max(ans, max(p1, p2) - min(p1, p2) - abs(i - x) - abs(y - j) - 1);
}
auto en = steady_clock().now();
time = duration_cast<milliseconds>(en - st).count();
// cout << time << "\n";
if(time >= 489)
break;
}
cout << ans;
}
