#include <iostream>
#include <vector>
#include <algorithm>
#define rep(i, s, e) for (ll i = s; i < e; i++)
#define upmax(a, b) a = max(a, b)
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
ll calc(vvll & arr, ll n, ll m) {
ll ans = -1;
vvll min_ele(n, vll(m, 1e18)), max_ele(n, vll(m, -2));
for (ll i = 0; i < n; i++) {
for (ll j = 0; j < m; j++) {
if (i > 0) {
min_ele[i][j] = min_ele[i - 1][j];
max_ele[i][j] = max_ele[i - 1][j];
}
if (j > 0) {
min_ele[i][j] = min(min_ele[i][j], min_ele[i][j - 1]);
max_ele[i][j] = max(max_ele[i][j], max_ele[i][j - 1]);
}
min_ele[i][j] = min(min_ele[i][j], arr[i][j] - i - j);
max_ele[i][j] = max(max_ele[i][j], arr[i][j] + i + j);
ans = max(ans, (arr[i][j] - i - j) - min_ele[i][j] - 1);
ans = max(ans, max_ele[i][j] - (arr[i][j] + i + j) - 1);
}
}
return ans;
}
void solve() {
ll n, m;
cin >> n >> m;
vvll arr(n, vll(m));
rep(i, 0, n) {
rep(j, 0, m) {
cin >> arr[i][j];
}
}
ll res = calc(arr, n, m);
rep(i, 0, n) {
reverse(arr[i].begin(), arr[i].end());
}
upmax(res, calc(arr, n, m));
cout << res << endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
}
