// Om Namah Shivaya
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x, y) ((x + y - 1) / (y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i, n) for(int i = 0; i < n; ++i)
#define rep1(i, n) for(int i = 1; i <= n; ++i)
#define rev(i, s, e) for(int i = s; i >= e; --i)
#define trav(i, a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a, b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a, b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
refs:
stress tested to identify the bug: https://oj.uz/submission/767335
didnt set the bounds for the binary search properly (wrote n instead of m)
*/
const int MOD = 1e9 + 7;
const int N = 2e3 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
ll n,m;
ll a[N][N], pmn[N][N], pmx[N][N], smn[N][N], smx[N][N];
ll ans = inf2;
vector<ll> lens;
void go(ll i, ll prev_len, ll mnl, ll mxl, ll mnr, ll mxr){
if(i > n){
ll val = max(mxl-mnl, mxr-mnr);
amin(ans,val);
// if(val == 19){
// debug(lens);
// }
return;
}
rep(j,m+1){
if(j < prev_len) conts;
ll mn1 = inf2, mx1 = -inf2;
ll mn2 = inf2, mx2 = -inf2;
rep1(k,m){
if(k <= j){
amin(mn1,a[i][k]);
amax(mx1,a[i][k]);
}
else{
amin(mn2,a[i][k]);
amax(mx2,a[i][k]);
}
}
lens.pb(j);
go(i+1, j, min(mnl,mn1), max(mxl,mx1), min(mnr,mn2), max(mxr,mx2));
lens.pop_back();
}
}
void solve(int test_case)
{
cin >> n >> m;
rep1(i,n) rep1(j,m) cin >> a[i][j];
memset(pmn,0x10,sizeof pmn);
memset(smn,0x10,sizeof smn);
memset(pmx,-0x10,sizeof pmx);
memset(smx,-0x10,sizeof smx);
rep1(i,n){
rep1(j,m){
pmn[i][j] = min(pmn[i][j-1], a[i][j]);
pmx[i][j] = max(pmx[i][j-1], a[i][j]);
}
rev(j,m,1){
smn[i][j] = min(smn[i][j+1], a[i][j]);
smx[i][j] = max(smx[i][j+1], a[i][j]);
}
}
vector<ll> b;
rep1(i,n){
rep1(j,m){
b.pb(a[i][j]);
}
}
sort(all(b));
b.resize(unique(all(b))-b.begin());
auto get = [&](ll mn, ll mx){
ll other_diff = inf2;
// dec
{
ll prev_len = inf2;
ll other_mn = inf2, other_mx = -inf2;
rep1(i,n){
ll len = 0;
ll l = 1, r = m;
while(l <= r){
ll mid = (l+r) >> 1;
if(pmn[i][mid] >= mn and pmx[i][mid] <= mx){
len = mid;
l = mid+1;
}
else{
r = mid-1;
}
}
amin(len,prev_len);
prev_len = len;
amin(other_mn, smn[i][len+1]);
amax(other_mx, smx[i][len+1]);
}
amin(other_diff, other_mx-other_mn);
}
// inc
{
ll prev_len = inf2;
ll other_mn = inf2, other_mx = -inf2;
rev(i,n,1){
ll len = 0;
ll l = 1, r = m;
while(l <= r){
ll mid = (l+r) >> 1;
if(pmn[i][mid] >= mn and pmx[i][mid] <= mx){
len = mid;
l = mid+1;
}
else{
r = mid-1;
}
}
amin(len,prev_len);
prev_len = len;
amin(other_mn, smn[i][len+1]);
amax(other_mx, smx[i][len+1]);
}
amin(other_diff, other_mx-other_mn);
}
return other_diff;
};
ll ans = inf2;
ll ptr = 0;
rep(ind,sz(b)){
amax(ptr,(ll) ind);
while(ptr < sz(b)){
ll res = get(b[ind], b[ptr]);
ll val = max(b[ptr]-b[ind], res);
amin(ans,val);
if(res <= b[ptr]-b[ind]){
break;
}
ptr++;
}
}
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
