#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 2e3+5;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll h, w;
int mx = 0, mn = mod;
int g[MAXN][MAXN], ot[MAXN][MAXN];
inline void turn(){
for(int i = 0; i < h; i++)
for(int j = 0; j < w; j++)
ot[j][h - 1 - i] = g[i][j];
swap(h, w);
for(int i = 0; i < h; i++)
for(int j = 0; j < w; j++)
g[i][j] = ot[i][j];
}
inline bool check(int del){
int sn = 0;
for(int i = 0; i < h; i++){
for(int j = 0; j < w; j++){
if(g[i][j] < mx - del)
sn = max(sn, j + 1);
}
for(int j = 0; j < sn; j++){
if(g[i][j] > mn + del)
return 0;
}
}
return 1;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
#ifdef Local
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
#endif
cin>>h>>w;
for(int i = 0; i < h; i++)
for(int j = 0; j < w; j++){
cin>>g[i][j];
mx = max(mx, g[i][j]);
mn = min(mn, g[i][j]);
}
int ans = mod;
int cn = 0;
do{
int l = 0, r = (int) 1e9;
while(l < r){
int m = (l + r) / 2;
if(check(m))
r = m;
else
l = m + 1;
}
ans = min(ans, l);
turn();
} while(++cn < 4);
cout<<ans<<endl;
#ifdef Local
cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
#endif
}
