//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,sse,sse2,sse3,ssse3,sse4,abm,popcnt,mmx")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
typedef long double ldb;
typedef complex<double> cd;
constexpr ll INF64 = 9'000'000'000'000'000'000, INF32 = 2'000'000'000, MOD = 1'000'000'007;
constexpr db PI = acos(-1);
constexpr bool IS_FILE = false, IS_TEST_CASES = false;
random_device rd;
mt19937 rnd32(rd());
mt19937_64 rnd64(rd());
template<typename T>
bool assign_max(T& a, T b) {
if (b > a) {
a = b;
return true;
}
return false;
}
template<typename T>
bool assign_min(T& a, T b) {
if (b < a) {
a = b;
return true;
}
return false;
}
template<typename T>
T square(T a) {
return a * a;
}
template<>
struct std::hash<pair<ll, ll>> {
ll operator() (pair<ll, ll> p) const {
return ((__int128)p.first * MOD + p.second) % INF64;
}
};
ll get(set<pair<ll, pair<ll, ll>>>& s) {
if (s.empty()) {
return 0;
}
return s.rbegin()->first - s.begin()->first;
}
ll sol(ll n, ll m, vector<vector<ll>>& arr) {
set<pair<ll, pair<ll, ll>>> s1, s2;
for (ll i = 0; i < n; i++) {
for (ll j = 0; j < m; j++) {
s1.emplace(arr[i][j], make_pair(i, j));
}
}
vector<ll> col(n, m - 1);
ll na = get(s1);
while (!s1.empty()) {
auto[x, y] = s1.rbegin()->second;
for (ll j = x; j < n; j++) {
if (col[j] < y) {
break;
}
while (col[j] >= y) {
s1.erase(make_pair(arr[j][col[j]], make_pair(j, col[j])));
s2.insert(make_pair(arr[j][col[j]], make_pair(j, col[j])));
col[j]--;
}
}
assign_min(na, max(get(s1), get(s2)));
}
return na;
}
void solve() {
ll n, m;
cin >> n >> m;
vector<vector<ll>> arr(n, vector<ll>(m));
for (ll i = 0; i < n; i++) {
for (ll j = 0; j < m; j++) {
cin >> arr[i][j];
}
}
ll ans = INF32;
for (ll i = 0; i < 2; i++) {
reverse(arr.begin(), arr.end());
for (ll j = 0; j < 2; j++) {
for (auto& k : arr) {
reverse(k.begin(), k.end());
}
assign_min(ans, sol(n, m, arr));
}
}
cout << ans << '\n';
}
int main() {
if (IS_FILE) {
freopen("", "r", stdin);
freopen("", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
ll t = 1;
if (IS_TEST_CASES) {
cin >> t;
}
for (ll i = 0; i < t; i++) {
solve();
}
}
