/*#pragma GCC optimize("O3")
#pragma GCC optimization("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")*/
#include <bits/stdc++.h>
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/
#define ll int
#define ll1 long long
#define ull unsigned long long
#define dou long double
#define str string
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vbool vector<bool>
#define vstr vector<str>
#define vvll vector<vll>
#define pb push_back
#define pf push_front
#define endl "\n"
#define fr first
#define se second
// #define sortcmp(a) sort(a.begin(), a.end(), cmp)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define INF 1000000007
#define ordered_set tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
//using namespace __gnu_pbds;
mt19937 rng(time(0));
ll randll(ll l, ll r) {
return uniform_int_distribution<ll>(l, r)(rng);
}
vvll pmx, pmn, smx, smn;
bool f(ll l, ll r, ll l1, ll r1, ll d, ll n, ll m, vvll& a) {
ll minl = m;
bool q = 1;
for (int i = 0; i < n; i ++) {
ll l_ = -1, r_ = minl;
while (r_ - l_ > 1) {
ll x = (l_+r_)/2;
if (pmx[i][x] <= r && pmn[i][x] >= l) l_ = x;
else r_ = x;
}
minl = r_;
if (r_ < m && (smx[i][r_] > r1 || smn[i][l_] < l1)){
q = 0;
break;
}
}
if (q) return 1;
q = 1;
minl = m;
for (int i = n-1; i >= 0; i --) {
ll l_ = -1, r_ = minl;
while (r_ - l_ > 1) {
ll x = (l_+r_)/2;
if (pmx[i][x] <= r && pmn[i][x] >= l) l_ = x;
else r_ = x;
}
minl = r_;
if (r_ < m && (smx[i][r_] > r1 || smn[i][r_] < l1)){
q = 0;
break;
}
}
if (q) return 1;
q = 1;
minl = -1;
for (int i = 0; i < n; i ++) {
ll l_ = minl, r_ = m;
while (r_ - l_ > 1) {
ll x = (l_+r_)/2;
if (smx[i][x] <= r && smn[i][x] >= l) r_ = x;
else l_ = x;
}
minl = l_;
if (l_ >= 0 && (pmx[i][l_] > r1 || pmn[i][l_] < l1)){
q = 0;
break;
}
}
if (q) return 1;
q = 1;
minl = -1;
for (int i = n-1; i >= 0; i --) {
ll l_ = minl, r_ = m;
while (r_ - l_ > 1) {
ll x = (l_+r_)/2;
if (smx[i][x] <= r && smn[i][x] >= l) r_ = x;
else l_ = x;
}
minl = l_;
if (l_ >= 0 && (pmx[i][l_] > r1 || pmn[i][l_] < l1)){
q = 0;
break;
}
}
if (q) return 1;
return 0;
}
int main(){
speed;
srand(time(0));
ll n, m;
cin >> n >> m;
vvll a(n, vll(m));
ll maxl = -INF, minl = INF;
for (int i =0 ; i < n; i ++) {
for (int j = 0; j < m; j ++) {
cin >> a[i][j];
maxl = max(maxl, a[i][j]);
minl = min(minl, a[i][j]);
}
}
pmx.resize(n, vll(m));
pmn.resize(n, vll(m));
smx.resize(n, vll(m));
smn.resize(n, vll(m));
for (int i = 0; i < n; i ++) {
pmx[i][0] = a[i][0];
pmn[i][0] = a[i][0];
smx[i][m-1] = a[i][m-1];
smn[i][m-1] = a[i][m-1];
for (int j = 1; j < m; j ++) {
pmx[i][j] = max(pmx[i][j-1], a[i][j]);
pmn[i][j] = min(pmn[i][j-1], a[i][j]);
}
for (int j = m-2; j >= 0; j --) {
smx[i][j] = max(smx[i][j+1], a[i][j]);
smn[i][j] = min(smn[i][j+1], a[i][j]);
}
}
ll l = -1, r = maxl-minl+1;
while (r-l > 1) {
ll x = (l+r)/2;
ll mx = minl+x;
if (f(minl, minl+x, maxl-x, maxl, x, n, m, a) || f(maxl-x, maxl, minl, minl+x, x, n, m, a)) r = x;
else l = x;
}
cout << r << endl;
}
