/*input
8 6
23 23 10 11 16 21
15 26 19 28 19 20
25 26 28 16 15 11
11 8 19 11 15 24
14 19 15 14 24 11
10 8 11 7 6 14
23 5 19 23 17 17
18 11 21 14 20 16
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
#pragma GCC optimize("unroll-loops,no-stack-protector")
//order_of_key #of elements less than x
// find_by_order kth element
using ll = long long;
using ld = long double;
using pii = pair<ll,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=1e9+7;
const ld PI=acos(-1);
const ld eps=1e-9;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
ll mult(ll a,ll b){
return a*b%MOD;
}
ll mypow(ll a,ll b){
if(b<=0) return 1;
ll res=1LL;
while(b){
if(b&1) res=(res*a)%MOD;
a=(a*a)%MOD;
b>>=1;
}
return res;
}
const ll maxn=2e3+5;
const ll maxlg=__lg(maxn)+2;
int mn=INF,mx=0;
int arr[4][maxn][maxn],tmp[maxn][maxn];
int n,m;
inline void rot(){
REP(asd,3){
REP(i,n){
REP(j,m){
tmp[m-j-1][i]=arr[asd][i][j];
}
}
swap(n,m);
REP(i,n) REP(j,m) arr[asd+1][i][j]=tmp[i][j];
}
swap(n,m);
}
inline bool wk(int mid){
int tn=n,tm=m;
REP(asd,4){
bool wk=1;
int pv=tm;
REP(i,tn){
REP(j,pv){
if(arr[asd][i][j]>mn+mid){
pv=j;
break;
}
}
for(int j=tm-1;j>=pv;j--){
if(arr[asd][i][j]<mx-mid){
wk=0;
break;
}
}
if(!wk) break;
}
if(wk){
return true;
}
swap(tn,tm);
}
return false;
}
int main(){
ios::sync_with_stdio(false),cin.tie(0);
cin>>n>>m;
REP(i,n) REP(j,m){
cin>>arr[0][i][j];
MNTO(mn,arr[0][i][j]);
MXTO(mx,arr[0][i][j]);
}
rot();
int l=0,r=mx-mn;
while(l<r){
int mid=(l+r)/2;
if(wk(mid)) r=mid;
else l=mid+1;
}
cout<<l;
}
