#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define y1 zck_is_king
#define pii pair<int, int>
#define ull unsigned ll
#define f first
#define s second
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
#define SQ(x) (x)*(x)
#define MN(a,b) a = min(a,(__typeof__(a))(b))
#define MX(a,b) a = max(a,(__typeof__(a))(b))
#define pb push_back
#define REP(i,n) for (int i = 0; i<n; ++i)
#define RREP(i,n) for (int i = n-1; i>=0; --i)
#define REP1(i,n) for (int i = 1; i<=n; ++i)
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#ifdef BALBIT
#define IOS()
#define bug(...) fprintf(stderr,"#%d (%s) = ",__LINE__,#__VA_ARGS__),_do(__VA_ARGS__);
template<typename T> void _do(T &&x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T &&x, S &&...y){cerr<<x<<", ";_do(y...);}
#else
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define bug(...)
#endif
const int iinf = 1e9+10;
const ll inf = 1ll<<60;
const ll mod = 1e9+7 ;
void GG(){cout<<"0\n"; exit(0);}
ll mpow(ll a, ll n, ll mo = mod){ // a^n % mod
ll re=1;
while (n>0){
if (n&1) re = re*a %mo;
a = a*a %mo;
n>>=1;
}
return re;
}
ll inv (ll b, ll mo = mod){
if (b==1) return b;
return (mo-mo/b) * inv(mo%b,mo) % mo;
}
const int maxn = 1e3+5;
int g[maxn][maxn];
ll h[maxn];
int n,m;
int re = 0;
void go() {
memset(h, 0x3f, sizeof h);
REP(i,n) REP(j,m) {
MN(h[j], g[i][j] - i - j);
if (j) MN(h[j], h[j-1]);
MX(re, g[i][j] - i - j - h[j]);
}
}
signed main(){
IOS();
cin>>n>>m;
REP(i,n) REP(j,m) {
cin>>g[i][j];
}
go();
REP(i,n) REP(j,m) {
if (j < m-1-j) swap(g[i][j], g[i][m-j-1]);
}
go();
REP(i,n) REP(j,m) {
if (i < n-1-i) swap(g[i][j], g[n-1-i][j]);
}
go();
REP(i,n) REP(j,m) {
if (j < m-1-j) swap(g[i][j], g[i][m-j-1]);
}
go();
cout<<re-1<<endl;
}
