#include <bits/stdc++.h>
#define respagold ios_base::sync_with_stdio(0), cin.tie(0);
#define ll long long
#define int long long
#define int2 __int128_t
#define FOR( i, x, n, d ) for( int i = x; i <= n; i += d )
#define FORR( i, x, n, d ) for( int i = x; i >= n; i -= d )
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x.size())
#define pb push_back
#define ins insert
#define lb lower_bound
#define ub upper_bound
#define pii pair <int, int>
#define mkp make_pair
using namespace std;
const int N = 1e6 + 123;
const int inf = 2e18;
const int MOD = 1e9 + 7;
const int MOD1 = 998244353;
const int P = 6547;
int a[N], b[N], c[N], n, m, x, y, z, w;
int mz[1005][1005], dp[1005][1005];
mt19937 rng( chrono::steady_clock::now().time_since_epoch().count());
int rand( int l, int r )
{
uniform_int_distribution <int> uid( l, r );
return uid( rng );
}
bool valid( int x, int y )
{
if( x < 1 || x > n || y < 1 || y > m ) return 0;
return 1;
}
void calc_dp( int x, int y, int dx, int dy )
{
int i = x, j = y;
while( valid(i, 1) )
{
j = y;
while( valid(1, j) )
{
dp[i][j] = min({ dp[i][j], dp[i - dx][j] + 1, dp[i][j - dy] + 1 });
j += dy;
}
i += dx;
}
}
void solve()
{
cin >> n >> m;
FOR( i, 1, n, 1 )
{
FOR( j, 1, m, 1 )
{
cin >> mz[i][j];
dp[i][j] = mz[i][j] + 1;
}
}
FOR( i, 0, m + 1, 1 ) dp[0][i] = inf, dp[n + 1][i] = inf;
FOR( i, 0, n + 1, 1 ) dp[i][0] = inf, dp[i][m + 1] = inf;
calc_dp( 1, 1, 1, 1 );
calc_dp( 1, m, 1, -1 );
calc_dp( n, 1, -1, 1 );
calc_dp( n, m, -1, -1 );
int ans = -1;
FOR( i, 1, n, 1 ) FOR( j, 1, m, 1 ) ans = max( ans, mz[i][j] - dp[i][j] );
cout << ans;
}
signed main()
{
// freopen("connect.in", "r", stdin);
// freopen("connect.out", "w", stdout);
respagold
int test = 1;
if( !test ) cin >> test;
while( test -- )
{
solve();
}
}
// solved by KluydQ
