#include <bits/stdc++.h>
//qwerty47924692
using namespace std;
using ll = long long;
const ll N=2005;
const string br="617283";
#define sz(a)(ll)a.size()
#define f first
#define s second
ll n,m,a[N][N],b[N][N],mn=1e18,mx=-1e18,c[N][N];
bool is_good(){
bool ok=1;
for(ll i=1;i<=n;i++){
for(ll j=1;j<=m;j++){
ok&=(c[i][j]&b[i][j])==(c[i][j]);
ok&=((c[i][j]>=c[i-1][j])&(c[i][j]>=c[i][j-1]));
}
}return ok;
}void clr(){
for(ll i=1;i<=n;i++){
for(ll j=1;j<=m;j++){
c[i][j]=2;
}
}
}
bool check(ll x){
for(ll i=1;i<=n;i++){
for(ll j=1;j<=m;j++){
b[i][j]=0;
b[i][j]|=(a[i][j]<=mn+x);
b[i][j]|=2*(a[i][j]>=mx-x);
if(!b[i][j])return 0;
}
}clr();
ll cur=m;
for(ll i=1;i<=n;i++){
for(ll j=1;j<=cur;j++){
if(!(b[i][j]&1)){
cur=j-1;
break;
}
c[i][j]=1;
}
}
if(is_good())return 1;
clr();
cur=m;
for(ll i=n;i>=1;i--){
for(ll j=1;j<=cur;j++){
if(!(b[i][j]&1)){
cur=j-1;
break;
}
c[i][j]=1;
}
}
if(is_good())return 1;
clr();
cur=n;
for(ll j=1;j<=m;j++){
for(ll i=1;i<=cur;i++){
if(!(b[i][j]&1)){
cur=i-1;
break;
}
c[i][j]=1;
}
}if(is_good())return 1;
clr();
cur=n;
for(ll j=m;j>=1;j--){
for(ll i=1;i<=cur;i++){
if(!(b[i][j]&1)){
cur=i-1;
break;
}
c[i][j]=1;
}
}if(is_good())return 1;
return 0;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin>>n>>m;
for(ll i=1;i<=n;i++){
for(ll j=1;j<=m;j++){
cin>>a[i][j];
mn=min(mn,a[i][j]);
mx=max(mx,a[i][j]);
}
}
ll l=1,r=1e9;
while(l<r){
ll mid=(r+l)>>1;
if(check(mid))r=mid;
else l=mid+1;
}
cout<<l;
}
