//Never stop trying
#include "bits/stdc++.h"
using namespace std;
#define boost ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
typedef long long ll;
typedef string str;
typedef long double ld;
typedef pair<int, int> pi;
#define fi first
#define se second
typedef vector<int> vi;
typedef vector<pi> vpi;
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define endl "\n"
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
const int MOD = 1e9 + 7; //998244353
const ll INF = 1e9;
const int MX = 2000 + 10;
const int nx[4] = {0, 0, 1, -1}, ny[4] = {1, -1, 0, 0}; //right left down up
template<class T> using V = vector<T>;
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
ll cdiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); } // divide a by b rounded up
//constexpr int log2(int x) { return 31 - __builtin_clz(x); } // floor(log2(x))
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
//mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
ll random(ll a, ll b){
return a + rng() % (b - a + 1);
}
#ifndef LOCAL
#define cerr if(false) cerr
#endif
#define dbg(x) cerr << #x << " : " << x << endl;
#define dbgs(x,y) cerr << #x << " : " << x << " / " << #y << " : " << y << endl;
#define dbgv(v) cerr << #v << " : " << "[ "; for(auto it : v) cerr << it << ' '; cerr << ']' << endl;
#define here() cerr << "here" << endl;
void IO() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
}
/////////////////////////ONLY CLEAN CODES ALLOWED/////////////////////////
int N,M,mn=INF,mx=-INF;
V<vi>g[4],gg;
bool solve(int d, int K){
int top=-1;
bool ok=1;
FOR(j,0,sz(g[d][0])){
ROF(i,0,sz(g[d])) if(!(g[d][i][j]>=mx-K)){
ckmax(top,i);
break;
}
FOR(i,0,top+1) if(!(g[d][i][j]<=mn+K)){
ok=0;
}
}
if(ok) return 1;
/*ok=1;
ROF(j,0,sz(g[d][0])){
ROF(i,0,sz(g[d])) if(!(g[d][i][j]>=mx-K)){
ckmax(top,i);
break;
}
FOR(i,0,top+1) if(!(g[d][i][j]<=mn+K)){
ok=0;
}
}*/
return ok;
}
void rotate(){
int n=sz(gg),m=sz(gg[0]);
V<vi>ggg;
ggg.resize(m);
FOR(i,0,m) ggg[i].resize(n);
FOR(i,0,n) FOR(j,0,m){
ggg[j][n-1-i]=gg[i][j];
}
gg.resize(m);
FOR(i,0,m) gg[i].assign(all(ggg[i]));
}
bool check(int K){
FOR(i,0,4){
if(solve(i,K)) return 1;
}
return 0;
}
void precompute(){
FOR(i,0,4){
g[i].resize(sz(gg));
FOR(r,0,sz(gg)){
g[i][r].assign(all(gg[r]));
}
rotate();
}
}
int main() {
boost; IO();
cin>>N>>M;
gg.resize(N);
FOR(i,0,N) gg[i].resize(M);
FOR(i,0,N) FOR(j,0,M){
cin>>gg[i][j];
ckmin(mn,gg[i][j]);
ckmax(mx,gg[i][j]);
}
precompute();
int l=0,r=mx-mn,ans;
while(l<=r){
int m=(l+r)/2;
if(check(m)){
ans=m;
r=m-1;
}
else l=m+1;
}
cout << ans << endl;
return 0;
}
//Change your approach
