// author : anhtun_hi , nqg
#include <bits/stdc++.h>
#define ll long long
#define ii pair<ll, ll>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define reset(h, v) memset(h, v, sizeof h)
#define Forv(i, a) for(auto& i : a)
#define For(i, a, b) for(int i = a; i <= b; ++i)
#define Ford(i, a, b) for(int i = a; i >= b; --i)
#define c_bit(i) __builtin_popcountll(i)
#define Bit(mask, i) ((mask >> i) & 1LL)
#define onbit(mask, i) ((mask) bitor (1LL << i))
#define offbit(mask, i) ((mask) &~ (1LL << i))
using namespace std;
namespace std {
template <typename T, int D>
struct _vector : public vector <_vector <T, D - 1>> {
static_assert(D >= 1, "Dimension must be positive!");
template <typename... Args>
_vector(int n = 0, Args... args) : vector <_vector <T, D - 1>> (n, _vector <T, D - 1> (args...)) {}
};
template <typename T> struct _vector <T, 1> : public vector <T> {
_vector(int n = 0, const T& val = T()) : vector <T> (n, val) {}
};
template <class A, class B> bool minimize(A &a, B b){return a > b ? a = b, true : false;}
template <class A, class B> bool maximize(A &a, B b){return a < b ? a = b, true : false;}
}
const int dx[] = {0, 0, +1, -1}, dy[] = {-1, +1, 0, 0}, LOG = 20, base = 311, inf = 1e9 + 5;
const int MAXN = 2e3 + 5;
const ll mod = 1e9 + 7;
const ll oo = 1e18;
//#define int long long
int n, m, mx, mn = inf; vector<vector<int>> a, b;
bool vs[MAXN][MAXN];
bool check(int val){
For(i, 0, n - 1){
For(j, 0, m - 1){
b[i][j] = 0;
if(a[i][j] <= mn + val) b[i][j] |= 1;
if(a[i][j] >= mx - val) b[i][j] |= 2;
if(b[i][j] == 0) return false;
}
}
// cerr << '*';
For(t, 1, 2){
bool ok = true;
int len = m - 1;
For(i, 0, n - 1){
int st = m, ed = -1;
For(j, 0, m - 1) if(b[i][j] == t) ed = j;
Ford(j, m - 1, 0) if(b[i][j] == (t ^ 3)) st = j;
minimize(len, st - 1);
if(len < ed) ok = false;
}
if(ok) return true;
ok = true;
len = m - 1;
Ford(i, n - 1, 0){
int st = m, ed = -1;
For(j, 0, m - 1) if(b[i][j] == t) ed = j;
Ford(j, m - 1, 0) if(b[i][j] == (t ^ 3)) st = j;
minimize(len, st - 1);
if(len < ed) ok = false;
}
if(ok) return true;
}
return false;
}
void Solve() {
cin >> n >> m;
a.assign(n, vector<int>(m, 0)), b.assign(n, vector<int>(m, 0));
For(i, 0, n - 1) For(j, 0, m - 1) cin >> a[i][j], minimize(mn, a[i][j]), maximize(mx, a[i][j]);
int l = -1, r = inf;
while(r - l > 1){
int mid = l + r >> 1;
if(check(mid)) r = mid;
else l = mid;
}
cout << r << '\n';
}
int32_t main() {
cin.tie(0) -> sync_with_stdio(0);
if(fopen("JOI17_joioi.inp", "r")) {
freopen("JOI17_joioi.inp", "r", stdin);
freopen("JOI17_joioi.out", "w", stdout);
}
int t = 1;
// cin >> t;
for (int test = 1; test <= t; test++) {
Solve();
}
return 0;
}
