#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;
typedef long long ll;
typedef long double ld;
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define st first
#define nd second
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define debug false
const int MAXW = 2000;
const ll MAXA = INT_MAX;
ll a[MAXW][MAXW];
ll a2[MAXW][MAXW];
bool jest[MAXW][MAXW];
ll maks, minn;
int w, h;
bool ok (ll d) {
for (int i = 0; i < w; i ++) {
for (int j = 0; j < h; j ++) {
jest[i][j] = false;
}
}
int poprzedni = h - 1;
bool rosnie = true;
for (int i = 0; i < w; i ++) {
int r = -1;
for (int j = 0; j <= poprzedni; j ++) {
if (a[i][j] - minn <= d) {
r = j;
jest[i][j] = true;
} else {
break;
}
}
poprzedni = r;
}
if (poprzedni == h - 1) {
return true;
}
ll aktmin = LLONG_MAX, aktmaks = 0;
for (int i = 0; i < w; i ++) {
for (int j = 0; j < h; j ++) {
if (!jest[i][j]) {
aktmin = min(aktmin, a[i][j]);
aktmaks = max(aktmaks, a[i][j]);
}
}
}
if (aktmaks - aktmin <= d) {
return true;
}
return false;
}
void obroc () {
for (int i = 0; i < h; i ++) {
for (int j = 0; j < w; j ++) {
a2[i][j] = a[j][i];
}
}
swap(w, h);
swap(a2, a);
for (int i = 0; i < w; i ++) {
for (int j = 0; j < h; j ++) {
cout << a[i][j] << " ";
}
cout << "\n";
}
cout << "\n";
}
ll licz () {
ll pocz = 0, kon = MAXA, wyn = 0;
while (pocz <= kon) {
ll sr = (pocz + kon)/ 2;
if (ok(sr)) {
wyn = sr;
kon = sr - 1LL;
} else {
pocz = sr + 1LL;
}
}
return wyn;
}
int main () {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> w >> h;
for (int i = 0; i < w; i ++) {
for (int j = 0; j < h; j ++) {
cin >> a[i][j];
}
}
maks = a[0][0];
minn = a[0][0];
for (int i = 0; i < w; i ++) {
for (int j = 0; j < h; j ++) {
maks = max(maks, a[i][j]);
minn = min(minn, a[i][j]);
}
}
ll rek = licz();
for (int i = 0; i < w; i ++) {
reverse(a[i], a[i] + h);
}
rek = min(rek, licz());
reverse(a, a + w);
rek = min(rek, licz());
for (int i = 0; i < w; i ++) {
reverse(a[i], a[i] + h);
}
rek = min(rek, licz());
cout << rek << "\n";
return 0;
}
