#pragma GCC diagnostic ignored "-Wunused-parameter"
#pragma GCC diagnostic ignored "-Wunused-variable"
#pragma GCC diagnostic ignored "-Wparentheses"
#include <bits/stdc++.h>
#define all(i) (i).begin(), (i).end()
#define random random_device rd; mt19937 rng(rd())
using namespace std;
template<typename T1, typename T2>
ostream& operator << (ostream &i, pair<T1, T2> j) {
return i << j.first << ' ' << j.second;
}
template<typename T>
ostream& operator << (ostream &i, vector<T> j) {
i << '{' << j.size() << ':';
for (T ii : j) i << ' ' << ii;
return i << '}';
}
void Debug(bool _split) {}
template<typename T1, typename ...T2>
void Debug(bool _split, T1 x, T2 ...args) {
if (_split)
cerr << ", ";
cerr << x, Debug(true, args...);
}
template<typename T>
void Debuga(T *i, int n) {
cerr << '[';
for (int j = 0; j < n; ++j) cerr << i[j] << " ]"[j == n - 1];
cerr << endl;
}
#ifdef SYL
#define debug(args...) cerr << "Line(" << __LINE__ << ") -> [" << #args << "] is [", Debug(false, args), cerr << ']' << endl
#define debuga(i) cerr << "Line(" << __LINE__ << ") -> [" << #i << "] is ", Debuga(i, sizeof(i) / sizeof(typeid(*i).name()))
#else
#define debug(args...) void(0)
#define debuga(i) void(0)
#endif
typedef long long ll;
typedef pair<int, int> pi;
const int inf = 0x3f3f3f3f, lg = 20;
const ll mod = 1e9 + 7, INF = 0x3f3f3f3f3f3f3f3f;
signed main() {
ios::sync_with_stdio(0), cin.tie(0);
int n, m;
cin >> n >> m;
int a[n][m];
ll dp[n][m], ans = -1;
for (int i = 0; i < n; ++i)
for (int j = 0; j < m; ++j)
cin >> a[i][j];
for (int i = 0; i < n; ++i)
for (int j = 0; j < m; ++j) {
dp[i][j] = a[i][j];
if (i)
dp[i][j] = max(dp[i][j], dp[i - 1][j] - 1);
if (j)
dp[i][j] = max(dp[i][j], dp[i][j - 1] - 1);
ans = max(ans, dp[i][j] - a[i][j] - 1);
}
for (int i = 0; i < n; ++i)
for (int j = m - 1; ~j; --j) {
dp[i][j] = a[i][j];
if (i)
dp[i][j] = max(dp[i][j], dp[i - 1][j] - 1);
if (j + 1 < m)
dp[i][j] = max(dp[i][j], dp[i][j + 1] - 1);
ans = max(ans, dp[i][j] - a[i][j] - 1);
}
for (int i = n - 1; ~i; --i)
for (int j = 0; j < m; ++j) {
dp[i][j] = a[i][j];
if (i + 1 < n)
dp[i][j] = max(dp[i][j], dp[i + 1][j] - 1);
if (j)
dp[i][j] = max(dp[i][j], dp[i][j - 1] - 1);
ans = max(ans, dp[i][j] - a[i][j] - 1);
}
for (int i = n - 1; ~i; --i)
for (int j = m - 1; ~j; --j) {
dp[i][j] = a[i][j];
if (i + 1 < n)
dp[i][j] = max(dp[i][j], dp[i + 1][j] - 1);
if (j + 1 < m)
dp[i][j] = max(dp[i][j], dp[i][j + 1] - 1);
ans = max(ans, dp[i][j] - a[i][j] - 1);
}
cout << ans;
}
