#include <bits/stdc++.h>
using namespace std;
const int N = 2005;
int n, m, mn = 1e9, a[N][N], b[N][N], f[N];
bool check0(int x) {
f[0] = 1e9;
int _mn, _mx;
_mn = 1e9, _mx = 0;
for (int i = 1; i <= n; ++i) {
int mx = 0; f[i] = 0;
for (int j = 1; j <= m; ++j) {
mx = max(mx, b[i][j]);
if (mx - mn > x) break;
f[i]++;
}
f[i] = min(f[i], f[i - 1]);
for (int j = f[i] + 1; j <= m; ++j) {
_mn = min(_mn, b[i][j]);
_mx = max(_mx, b[i][j]);
}
}
return _mx - _mn <= x;
}
bool check1(int x) {
bool ok = 0;
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
b[i][j] = a[i][j];
}
}
ok |= check0(x);
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
b[i][j] = a[i][m - j + 1];
}
}
ok |= check0(x);
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
b[i][j] = a[n - i + 1][j];
}
}
ok |= check0(x);
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
b[i][j] = a[n - i + 1][m - j + 1];
}
}
ok |= check0(x);
return ok;
}
int main() {
ios::sync_with_stdio(false);
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 = 1e9;
while (l < r) {
int mid = (l + r) >> 1;
if (check1(mid)) r = mid;
else l = mid + 1;
}
cout << l;
}
