#include <iostream>
#include <map>
using namespace std;
int main()
{
int n, m;
cin >> n >> m;
multimap<int, pair<int, int>> matrix;
int x;
for(int i = 0; i < n; i++) for(int j = 0; j < m; j++)
{
cin >> x;
matrix.emplace(x, pair<int, int>(i, j));
}
int w = 0;
for(auto it = matrix.begin(); it != matrix.end(); it++) for(auto itt = matrix.begin(); itt != matrix.end(); itt++)
{
w = max(w, abs(it->first - itt->first) - abs(it->second.first - itt->second.first) - abs(it->second.second - itt->second.second) - 1);
}
cout << w << "\n";
return 0;
}
