#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <set>
using namespace std;
typedef long long ll;
const int N = 2024;
int a[N][N];
bool used[N][N];
int n, m;
int mn;
bool f(int d) {
int mn = 1e9 + 10, mx = 0;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
if (!used[i][j]) {
mx = max(mx, a[i][j]);
mn = min(mn, a[i][j]);
}
}
}
if ((mx - mn) <= d) return true;
return false;
}
bool ch(int d) {
int last_h = n;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
used[i][j] = false;
}
}
for (int j = m; j >= 1; j--) {
for (int i = n; i >= n - last_h + 1; i--) {
if (a[i][j] > (mn + d)) {
last_h = n - i;
break;
}
used[i][j] = true;
}
}
if (f(d)) return true;
last_h = n;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
used[i][j] = false;
}
}
for (int j = 1; j <= m; j++) {
for (int i = n; i >= n - last_h + 1; i--) {
if (a[i][j] > (mn + d)) {
last_h = n - i;
break;
}
used[i][j] = true;
}
}
if (f(d)) return true;
last_h = n;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
used[i][j] = false;
}
}
for (int j = 1; j <= m; j++) {
for (int i = 1; i <= last_h; i++) {
if (a[i][j] > (mn + d)) {
last_h = i - 1;
break;
}
used[i][j] = true;
}
}
if (f(d)) return true;
last_h = n;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
used[i][j] = false;
}
}
for (int j = m; j >= 1; j--) {
for (int i = 1; i <= last_h; i++) {
if (a[i][j] > (mn + d)) {
last_h = i - 1;
break;
}
used[i][j] = true;
}
}
if (f(d)) return true;
return false;
}
int main() {
mn = 1000000010;
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
mn = min(mn, a[i][j]);
}
}
int l = 0, r = 1000000010, ans = -1;
while (l <= r) {
int mid = (l + r) / 2;
if (ch(mid)) {
ans = mid;
r = mid - 1;
}
else l = mid + 1;
}
cout << ans << "\n";
}
