#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template <class T, class ...U>
void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template <class T>
void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l) == r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
template <class T>
bool chmin(T &a, T b) { return b < a ? (a = b, true) : false; }
template <class T>
bool chmax(T &a, T b) { return a < b ? (a = b, true) : false; }
const int MAX_N = 2010, inf = 1e9;
//#define int ll
int n, m, a[MAX_N][MAX_N], res = inf;
int pfmx[MAX_N][MAX_N];
//struct bit {
// vector<vector<int>> v;
// int n, m;
// bit(int _n, int _m) :
// n(_n), m(_m) {
// v.resize(n+1, vector<int>(m+1));
// }
//
// void add(int x, int y) {
// for (int i = x;i <= n;i += i&-i)
// for (int j = y;j <= m;j += j&-j)
// ++v[i][j];
// }
// int qry(int x, int y) {
// int res = 0;
// for (int i = x;i;i ^= i&-i)
// for (int j = y;j;j ^= j&-j)
// res += v[i][j];
// return res;
// }
//};
void update() {
//bit tree(n, m);
vector<pair<int,int>> id;
id.reserve(n * m);
for (int i = 1;i <= n;++i)
for (int j = 1;j <= m;++j) {
pfmx[i][j] = max({pfmx[i-1][j], pfmx[i][j-1], a[i][j]});
id.pb(i, j);
}
auto get = [&](pair<int,int> p) {
return a[p.first][p.second];
};
sort(AI(id), [&](auto x, auto y) {
return get(x) < get(y);
});
for (int i = 0, j = 0;i+1 < id.size();++i) {
auto valid = [&](pair<int,int> p) {
return pfmx[p.first][p.second] <= get(id[i]);
};
while (j <= i && valid(id[j]))
++j;
if (valid(id[0]) && valid(id[i]))
chmin(res, max(get(id[i]) - get(id[0]), get(id.back()) - get(id[j])));
}
chmin(res, get(id.back()) - get(id.front()));
}
int32_t main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> m;
for (int i = 1;i <= n;++i)
for (int j = 1;j <= m;++j)
cin >> a[i][j];
update();
for (int l = 1, r = n;l < r;++l, --r)
swap(a[l], a[r]);
update();
for (int i = 1;i <= n;++i) {
for (int l = 1, r = m;l < r;++l, --r)
swap(a[i][l], a[i][r]);
}
update();
for (int l = 1, r = n;l < r;++l, --r)
swap(a[l], a[r]);
update();
cout << res << '\n';
}
