#include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10
#define ll long long
#define double long double
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define aint(a) (a).begin(), (a).end()
#define f first
#define s second
#define pb push_back
#define mp make_pair
#define pi pair
#define rc(s) return cout<<s,0
#define endl '\n'
#define mod 1000000007
#define PI 3.14159265359
#define MAXN 100005
#define INF 1000000005
#define LINF 1000000000000000005ll
#define CODE_START ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll n,m,a[1005][1005],pref[1005][1005],ans=0;
void change(ll n,ll m){
for(ll i=1;i<=max(n,m);i++)
{
for(ll j=i+1;j<=max(n,m);j++)
{
swap(a[i][j],a[j][i]);
}
}
for(ll i=1;i<=m;i++)
{
for(ll j=1;j<=n/2;j++)
{
swap(a[i][j],a[i][n-j+1]);
}
}
return;
}
int32_t main(){
CODE_START;
cin>>n>>m;
for(ll i=1;i<=n;i++)
{
for(ll j=1;j<=m;j++){
cin>>a[i][j];
}
}
for(ll i=0;i<=max(n,m);i++)
{
pref[i][0]=LINF;
pref[0][i]=LINF;
}
for(ll i=1;i<=n;i++)
{
for(ll j=1;j<=m;j++){
pref[i][j]=min(pref[i-1][j],min(pref[i][j-1],a[i][j]-i-j));
ans=max(ans,a[i][j]-i-j-min(pref[i-1][j],pref[i][j-1]));
}
}
change(n,m);
for(ll i=1;i<=n;i++)
{
for(ll j=1;j<=m;j++){
pref[i][j]=min(pref[i-1][j],min(pref[i][j-1],a[i][j]-i-j));
ans=max(ans,a[i][j]-i-j-min(pref[i-1][j],pref[i][j-1]));
}
}
change(m,n);
for(ll i=1;i<=n;i++)
{
for(ll j=1;j<=m;j++){
pref[i][j]=min(pref[i-1][j],min(pref[i][j-1],a[i][j]-i-j));
ans=max(ans,a[i][j]-i-j-min(pref[i-1][j],pref[i][j-1]));
}
}
change(n,m);
for(ll i=1;i<=n;i++)
{
for(ll j=1;j<=m;j++){
pref[i][j]=min(pref[i-1][j],min(pref[i][j-1],a[i][j]-i-j));
ans=max(ans,a[i][j]-i-j-min(pref[i-1][j],pref[i][j-1]));
}
}
cout<<ans-1<<endl;
}
