#include<bits/stdc++.h>
#pragma GCC optimize("unroll-loops,no-stack-protector")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
const ll MOD=1e9+7;
const ll MOD2=998244353;
const ll N=2e3+5;
const ld pi=3.14159265359;
const ll INF=(1LL<<60);
#define SQ(i) ((i)*(i))
#define REP(i,n) for(ll i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define setp setprecision
#define lwb lower_bound
#define SZ(_a) (ll)_a.size()
ll n,m,mn,mx,u[N][N],ans;
bool ok(ll k){
ll h=m;
REP(i,n){
ll id=0;
while(u[i][id]-mn<=k&&id<h)++id;;
h=id;
for(int j=id;j<m;j++)if(mx-u[i][j]>k)return 0;
}
return 1;
}
ll solve(){
ll tmp=0;
for(int i=31;i>=0;i--){
if(!ok(tmp+(1LL<<i)))tmp+=(1LL<<i);
}
return tmp+1;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n>>m;
mn=INF;mx=-INF;
REP(i,n)REP(j,m)cin>>u[i][j],mn=min(mn,u[i][j]),mx=max(mx,u[i][j]);
ans=solve();
reverse(u,u+n);
ans=min(ans,solve());
REP(i,n)reverse(u[i],u[i]+m);
ans=min(ans,solve());
reverse(u,u+n);
ans=min(ans,solve());
cout<<ans<<"\n";
return 0;
}
