#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = 2e3 + 5, inf = 1e9;
int n, m, mn = inf, mx;
int a[N][N];
bool check(int k) {
int cut = 0;
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m; ++j) {
if (a[i][j] < mx - k) {
cut = max(cut, j);
}
}
for (int j = 1; j <= m; ++j) {
if (a[i][j] > mn + k && cut >= j) {
return 0;
}
}
}
return 1;
}
int solve() {
int L = 0, R = mx - mn, res = mx - mn;
while (L <= R) {
int md = (L + R) / 2;
if (check(md)) {
res = md;
R = md - 1;
} else {
L = md + 1;
}
}
return res;
}
void flip_row() {
for (int j = 1; j <= m; ++j) {
for (int i = 1; i <= n / 2; ++i) {
swap(a[i][j], a[n - i + 1][j]);
}
}
}
void flip_col() {
for (int i = 1; i <= n; ++i) {
for (int j = 1; j <= m / 2; ++j) {
swap(a[i][j], a[i][m - j + 1]);
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
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]);
mx = max(mx, a[i][j]);
}
}
int res = solve();
flip_row();
res = min(res, solve());
flip_col();
res = min(res, solve());
flip_row();
res = min(res, solve());
cout << res;
return 0;
}
