#include<bits/stdc++.h>
using namespace std;
#define foru(i,a,b) for(int i=(a); i<=(b); ++i)
#define ford(i,a,b) for(int i=(a); i>=(b); --i)
#define rep(i,a) for(int i=0; i<(a); ++i)
#define sz(a) (int)(a).size()
#define all(a) (a).begin(),(a).end()
#define bit(s,i) (((s)>>(i))&1)
#define ii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define ll long long
#define _ << " " <<
template <class X, class Y> bool maxi(X &x, Y y){return x<y?x=y,true:false;}
template <class X, class Y> bool mini(X &x, Y y){return x>y?x=y,true:false;}
const int N=2020;
const int INF=1e9;
int h,w,a[N][N],mi=INF,mx=0;
bool oka[N][N],okb[N][N];
bool chk(int diff){
foru(i,1,h){
foru(j,1,w){
if(a[i][j]-mi<=diff) oka[i][j]=1;
else oka[i][j]=0;
if(mx-a[i][j]<=diff) okb[i][j]=1;
else okb[i][j]=0;
}
}
int lstI=0, lstD=w, l, r, cnt;
foru(i,1,h){
l=w+1, r=-1, cnt=0;
foru(j,1,w) cnt+=okb[i][j];
if(cnt==w) l=0, r=0;
foru(j,1,w){
cnt=cnt-okb[i][j]+oka[i][j];
if(cnt==w) mini(l,j), maxi(r,j);
}
if(l==w+1){
lstI=lstD=-1;
break;
}
if(lstI!=-1){
if(r<lstI){
lstI=-1;
} else if(l<=lstI){
lstI=lstI;
} else if(l>lstI){
lstI=l;
} else{
assert(0);
}
}
if(lstD!=-1){
if(l>lstD){
lstD=-1;
} else if(r>=lstD){
lstD=lstD;
} else if(r<lstD){
lstD=r;
} else{
assert(0);
}
}
}
if(lstI!=-1||lstD!=-1) return true;
lstI=0, lstD=w;
foru(i,1,h){
l=w+1, r=-1, cnt=0;
foru(j,1,w) cnt+=oka[i][j];
if(cnt==w) l=0, r=0;
foru(j,1,w){
cnt=cnt-oka[i][j]+okb[i][j];
if(cnt==w) mini(l,j), maxi(r,j);
}
if(l==w+1){
lstI=lstD=-1;
break;
}
if(lstI!=-1){
if(r<lstI){
lstI=-1;
} else if(l<=lstI){
lstI=lstI;
} else if(l>lstI){
lstI=l;
} else{
assert(0);
}
}
if(lstD!=-1){
if(l>lstD){
lstD=-1;
} else if(r>=lstD){
lstD=lstD;
} else if(r<lstD){
lstD=r;
} else{
assert(0);
}
}
}
if(lstI!=-1||lstD!=-1) return true;
return false;
}
void solve(){
cin>>h>>w;
foru(i,1,h) foru(j,1,w){
cin>>a[i][j];
mini(mi,a[i][j]);
maxi(mx,a[i][j]);
}
int l=0,r=1e9,res=1e9;
while(l<=r){
int m=(l+r)>>1;
if(chk(m)){
r=m-1;
res=m;
}else{
l=m+1;
}
}
cout<<res<<'\n';
}
int32_t main(){
#define task "test"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin.tie(0)->sync_with_stdio(0);
int tc=1; //cin>>tc;
rep(i,tc){
solve();
}
}
