#include <bits/stdc++.h>
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int n, m;
std::cin >> n >> m;
std::vector<std::vector<int64_t>> a(n + 1, std::vector<int64_t>(m + 1));
for(int i = 1; i <= n; i++) {
for(int j = 1; j <= m; j++) {
std::cin >> a[i][j];
}
}
int64_t ans = 0;
for(int x = 1; x <= n; x++) {
for(int y = 1; y <= m; y++) {
for(int x1 = 1; x1 <= n; x1++) {
for(int y1 = 1; y1 <= m; y1++) {
int64_t cost = a[x][y] - a[x1][y1];
int64_t path = abs(x - x1) + abs(y - y1) + 1;
ans = std::max(ans, cost - path);
}
}
}
}
std::cout << ans;
}
