#include<bits/stdc++.h>
using namespace std;
#define debug(x) cout << '[' << #x << " is: " << x << "] " << endl;
#define inF freopen("6in.txt" , "r" , stdin);
#define outF freopen("6.txt" , "w" , stdout);
#define imod(a , n) (a % n + n ) % n
#define sor(v) sort(v.begin() , v.end());
#define print(v) for(auto f : v ) cout << f << " " ;
#define rsor(v) sort(v.rbegin() , v.rend());
#define rev(v) reverse(v.begin() , v.end());
#define scan(v)for(auto &it : v)cin >> it ;
#define ll long long
#define int ll
#define logar(x , y) log(x) / log(y)
#define __sum(n) n * (n + 1) / 2
#define __lcm(a , b) a / __gcd(a , b) * b
#define pii pair<int , int >
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);
const int N = 2e3 + 5 ;
set<int> st ;
vector<int> v ;
int n , m ;
int arr[N][N];
int sz ;
int MN[N][N] , MXY[N][N] ,RMN[N][N] , RMX[N][N];
bool check(int from , int to){
int mx = 0 , mn = 1e9 , en = n;
//cout << from << " " << to << endl ;
for(int c = 0 ; c < m ; c ++){
int l = 0 , r = en - 1, md ;
int ans = -1 ;
int cnt = 0 ;
while(l <= r){
cnt ++ ;
if(cnt == 15)break;
md = (l + r) / 2;
//debug(MXY[md][c])
if(MN[md][c] >= from && MXY[md][c] <= to){
ans = md , l = md +1 ;
}
else r = md - 1 ;
// if(n + m > 2000)break;
} en = min(en , ans + 1);
// debug(ans)
// debug(en)
if(en != n )mx = max(mx ,RMX[en][c]) , mn= min(mn ,RMN[en][c]);
}
return mx-mn <= to - from;
}
void process(){
for(int j = 0 ;j < m;j ++){
for(int i = 0 ; i < n ; i ++){
MN[i][j]= arr[i][j] , MXY[i][j] = arr[i][j];
if(i)MN[i][j] = min(MN[i][j] , MN[i - 1][j]) , MXY[i][j] = max(MXY[i - 1][j] , MXY[i][j]);
}
}
for(int j = 0 ; j < m ; j ++){
for(int i = n - 1 ; i >= 0 ; i --){
RMN[i][j]= arr[i][j] , RMX[i][j] = arr[i][j];
if(i != n - 1)RMN[i][j] = min(RMN[i][j] , RMN[i + 1][j]) , RMX[i][j] = max(RMX[i + 1][j] , RMX[i][j]);
}
}
}
int arr2[N][N];
int32_t main()
{ //inF;
//inF;outF;
fastio;
cin >> n >> m ;
for(int i = 0 ; i < n; i ++){
for(int j = 0 ; j <m; j ++){
cin >> arr[i][j];
arr2[i][j] = arr[i][j];
st.insert(arr[i][j]);
}
}
for(auto f : st)v.push_back(f);
process();
sz = v.size();
ll mnans = v.back() - v[0];
for(int all = 0 ; all < 2 ; all ++){
int l = 0 , r = 1e9 , md ;
int cnt = 0 ;
while(l <= r){
cnt ++ ;
if(cnt == 32)break;
md = (l + r) / 2 ;
if(check(v[0] , v[0] + md) || check(v.back() - md , v.back()))mnans = min(mnans , md) , r = md- 1 ;
else l = md + 1 ;
}
for(int c = 0 ; c < m ; c ++){
for(int r = 0 ; r< n ; r ++){
arr[r][c] = arr2[r][m - 1 - c];
// debug(arr[r][c])
}
}
process();
}
cout << mnans ;
}
