#include<bits/stdc++.h>
#define F first
#define S second
#define SZ(x) ((ll)(x).size())
inline void outlast() {
#ifndef ONLINE_JUDGE
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
}
const char nl = '\n';
using namespace std;
using ll = long long;
// head
const ll N = 2100;
vector<vector<ll>> a(N, vector<ll> (N, 0));
ll h, w;
vector<vector<ll>> CIRCLE(const vector<vector<ll>>& matrix) {
vector<vector<ll>> rotated(N, vector<ll>(N));
for (ll i = 1; i <= h; i++) {
for (ll j = 1; j <= w; j++) {
rotated[j][h-i+1] = matrix[i][j];
}
}
swap(h, w);
return rotated;
}
void solve() {
cin >> h >> w;
for (ll i = 1; i <= h; i ++) {
for (ll j = 1; j <= w; j ++) {
cin >> a[i][j];
}
}
ll L = 0, R = 1e9;
while (L + 1 < R) {
ll mid = (L + R) / 2;
bool ok = false;
for (ll i = 0; i < 4; i ++) {
a = CIRCLE(a);
ll val = LLONG_MAX, posx = 0, posy = 0;
for (ll i = 1; i <= h; i ++) {
for (ll j = 1; j <= w; j ++) {
if (a[i][j] < val) {
val = a[i][j];
posx = i;
posy = j;
}
}
}
vector<ll> row(N, 0);
for (ll i = 1; i <= h; i ++) {
for (ll j = 1; j <= w; j ++) {
if (a[i][j] <= val + mid) {
row[i] ++;
} else {
break;
}
}
}
for (ll i = 2; i <= h; i ++) {
row[i] = min(row[i], row[i-1]);
}
ll mn = LLONG_MAX, mx = LLONG_MIN;
for (ll i = 1; i <= h; i ++) {
for (ll j = row[i]+1; j <= w; j ++) {
mn = min(mn, a[i][j]);
mx = max(mx, a[i][j]);
}
}
if (row[posx] >= posy && (mx == LLONG_MIN || mx - mn <= mid)) {
ok = true;
}
}
if (ok) {
R = mid;
} else {
L = mid;
}
}
cout << R;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
// outlast();
ll tst = 1;
// cin >> tst;
while (tst --) {
solve();
cout << nl;
}
}
