#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define rep(a,b,c) for(int a=b; a<c; a++)
#define repr(a,b,c) for(int a=b-1; a>c-1; a--)
#define repa(a,b) for(auto a:b)
#define mid ((l+r)>>1)
#define endl "\n"
using namespace std;
using vi = vector<int>;
const int N=2005, inf=1e9+5;
int h, w, g[N][N], pf[N][N][2][2], ans;
void solve(int x, int y, int a, int b, int mn, int mn2){
int z;
if(x==0) z=1;
else z=-1;
int mx=0, lst;
if(y) lst=0;
else lst=w;
rep(i,0,h){
int l=0, r=w-1;
while(l<=r){
if(!y){
if(pf[x][mid][0][0]>=mn) l=mid+1;
else r=mid-1;
}else{
if(pf[x][mid][1][0]>=mn) r=mid-1;
else l=mid+1;
}
}
if(!y){
l=min(l,lst);
r=l-1;
if(x==a && b>=l) return;
mx=max({mx,pf[x][r][0][1]-mn,pf[x][l][1][1]-mn2});
}else{
l=max(l,lst);
r=l-1;
if(x==a && b<=r) return;
mx=max({mx,pf[x][l][1][1]-mn,pf[x][r][0][1]-mn2});
}
x+=z;
lst=l;
}
ans=min(ans,mx);
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>h>>w;
int mn=inf, mx=-inf, x, y;
rep(i,0,h) rep(j,0,w){
cin>>g[i][j];
mn=min(mn,g[i][j]);
mx=max(mx,g[i][j]);
}
ans=mx-mn;
rep(i,0,h){
x=inf;
y=-inf;
rep(j,0,w) x=min(x,g[i][j]), y=max(y,g[i][j]), pf[i][j][0][0]=x, pf[i][j][0][1]=y;
x=inf;
y=-inf;
repr(j,w,0) x=min(x,g[i][j]), y=max(y,g[i][j]), pf[i][j][1][0]=x, pf[i][j][1][1]=y;
}
rep(i,0,h) rep(j,0,w){
if(g[i][j]==mn) continue;
solve(0,0,i,j,g[i][j],mn);
solve(0,w-1,i,j,g[i][j],mn);
solve(h-1,0,i,j,g[i][j],mn);
solve(h-1,w-1,i,j,g[i][j],mn);
}
cout<<ans<<endl;
}
