#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define LL long long
#define st first
#define nd second
#define endl '\n'
using namespace std;
const int MAXN=2005;
int a[MAXN][MAXN],n,m,ans=1e9,mx,mn,idx,l,r,add,mnn,b[MAXN][MAXN];
multiset<int> mpp;
void rotate1() {
//cout<<"fuk"<<endl;
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
b[i][m-j-1]=a[i][j];
}
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
a[i][j]=b[i][j];
}
}
void rotate2() {
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
b[n-i-1][j]=a[i][j];
}
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
a[i][j]=b[i][j];
}
}
int solve() {
/*for(int i=0;i<n;++i) {
for(int j=0;j<m;++j) {
cout<<a[i][j]<<" ";
}
cout<<endl;
}*/
int ret=1e9;
int x,y;
mn=1e9+1;
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
mpp.insert(a[i][j]);
if(mn>a[i][j]) {
mn=a[i][j];
x=i;
y=j;
}
}
//cout<<"xd"<<endl;
mx=0;
//cout<<x<<" "<<y<<" "<<mpp.size()<<endl;
int up[MAXN];
int cnt=0;
memset(up,0,sizeof up);
for(int j=0;j<=x;++j) {
up[j]=y+1;
for(int i=0;i<=y;++i) {
mx=max(mx,a[j][i]);
mpp.erase(mpp.find(a[j][i]));
++cnt;
}
}
if(mpp.size()) ret=min(ret,max(mx-mn,*(--mpp.end())-*mpp.begin()));
priority_queue<pii> pq;
for(int i=0;i<n;++i) {
if(up[i]!=m) {
if(i&&up[i]==up[i-1])
continue;
pq.push(mp(-a[i][up[i]],i));
}
}
//cout<<"xd"<<endl;
pii dd;
int val;
while(!mpp.empty()) {
//cout<<pq.size()<<" "<<up[1]<<endl;
add=-1,mnn=1e9+1;
dd=pq.top();
pq.pop();
add=dd.nd;
val=-dd.st;
mx=max(mx,val);
mpp.erase(mpp.find(val));
++up[add];
//cout<<add<<" "<<up[add]<<" "<<up[1]<<endl;
if(up[add]!=m) {
if(add!=0&&up[add]==up[add-1]);
else pq.push(mp(-a[add][up[add]],add));
}
//cout<<up[add+1]<<" "<<add+1<<" "<<up[1]<<endl;
if(add+1!=n&&up[add+1]==up[add]-1)
pq.push(mp(-a[add+1][up[add+1]],add+1));
//cout<<mpp.size()<<endl;
if(!mpp.empty()) ret=min(ret,max(mx-mn,*(--mpp.end())-*mpp.begin()));
//cout<<mpp.size()<<endl;
}
//cout<<"rekt"<<endl;
return ret;
}
int main() {
scanf("%d %d",&n,&m);
for(int i=0;i<n;++i)
for(int j=0;j<m;++j) {
scanf("%d",&a[i][j]);
}
ans=min(ans,solve());
rotate1();
//cout<<"malahmet"<<endl;
ans=min(ans,solve());
rotate2();
ans=min(ans,solve());
rotate1();
ans=min(ans,solve());
printf("%d\n",ans);
}
