/**
____ ____ ____ __________________ ____ ____ ____
||I || ||c || ||e || || || ||M || ||a || ||n ||
||__|| ||__|| ||__|| ||________________|| ||__|| ||__|| ||__||
|/__\| |/__\| |/__\| |/________________\| |/__\| |/__\| |/__\|
*/
#include <iostream>
#include <chrono>
#include <vector>
///#include "grader.h"
#define maxn 1005
#define maxlog 20
#define INF 1000000010
#define LINF 1000000000000000005
#define endl '\n'
#define pb(x) push_back(x)
#define X first
#define Y second
#define control cout<<"passed"<<endl;
#pragma GCC optimize("O3" , "Ofast" , "unroll-loops" , "fast-math")
#pragma GCC target("avx2")
using namespace std;
typedef unsigned long long ull;
typedef pair <int, int> pii;
typedef long long ll;
typedef pair <ll, ll> pll;
typedef pair <int, ll> pil;
typedef pair <ll, int> pli;
typedef long double pd;
int n, m;
int a[maxn][maxn];
void read()
{
cin >> n >> m;
for(int i = 1; i <= n; i++)
for(int j = 1; j <= m; j++)
cin >> a[i][j];
}
int dp[maxn][maxn];
int ans = -INF;
void _try()
{
for(int i = 1; i <= n; i++)
for(int j = 1; j <= m; j++)
{
dp[i][j] = a[i][j];
if(i > 1)
dp[i][j] = max(dp[i][j], dp[i - 1][j] - 1);
if(j > 1)
dp[i][j] = max(dp[i][j], dp[i][j - 1] - 1);
ans = max(ans, dp[i][j] - a[i][j] - 1);
}
}
void solve()
{
ans = -INF;
_try();
for(int i = 1; i <= n / 2; i++)
for(int j = 1; j <= m; j++)
swap(a[i][j] , a[n - i + 1][j]);
/**cout << "-------------------------" << endl;
for(int i = 1; i <= n; i++ , cout << endl)
for(int j = 1; j <= m; j++)
cout << a[i][j] << " ";*/
_try();
for(int i = 1; i <= n; i++)
for(int j = 1; j <= m / 2; j++)
swap(a[i][j] , a[i][m - j + 1]);
/**cout << "-------------------------" << endl;
for(int i = 1; i <= n; i++ , cout << endl)
for(int j = 1; j <= m; j++)
cout << a[i][j] << " ";*/
_try();
for(int i = 1; i <= n / 2; i++)
for(int j = 1; j <= m; j++)
swap(a[i][j] , a[n - i + 1][j]);
/**cout << "-------------------------" << endl;
for(int i = 1; i <= n; i++ , cout << endl)
for(int j = 1; j <= m; j++)
cout << a[i][j] << " ";*/
_try();
cout << ans << endl;
}
int main()
{
/**#ifdef ONLINE_JUDGE /// promeni
freopen("taxi.in", "r", stdin);
freopen("taxi.out", "w", stdout);
#endif*/
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
///startT = std::chrono::high_resolution_clock::now();
read();
solve();
return 0;
}
