#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vb = vector<bool>;
using vvb = vector<vb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vc = vector<char>;
using vvc = vector<vc>;
using vs = vector<string>;
const ll mod = 1e9 + 7,inf = 1e18;
#define pb push_back
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
void setIO()
{
fast;
}
int main()
{
setIO();
int n,m;
cin>>n>>m;
vvi a(n + 1,vi(m + 1)),dp(n + 1,vi(m + 1));
for (int i = 1;i<=n;i++)for (int j = 1;j<=m;j++)cin>>a[i][j];
for (int i = 1;i<=n;i++){
for (int j = 1;j<=m;j++){
dp[i][j] = a[i][j] - 1;
dp[i][j] = max(dp[i][j],dp[i - 1][j] - 1);
dp[i][j] = max(dp[i][j],dp[i][j - 1] - 1);
}
}
for (int i = n;i>=1;i--){
for (int j = m;j>=1;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);
}
}
int ans = dp[1][1] - a[1][1];
for (int i = 1;i<=n;i++)
for (int j = 1;j<=m;j++)
ans = max(ans,dp[i][j] - a[i][j]);
cout<<ans;
return 0;
}
