#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
using tll = tuple<ll, ll, ll, ll>;
inline void fastio() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
}
const ll INF = 1e18;
ll h, w, mn = INF, mx, ans = INF;
vector<vector<ll>> v;
bool chk(ll val) {
for (ll i = 0, tmp = 0; i < h; i++) {
for (ll j = 0; j < w; j++) if (v[i][j] + val < mx) {
tmp = max(tmp, j + 1);
}
for (ll j = 0; j < w; j++) if (v[i][j] > mn + val and j < tmp) {
return false;
}
}
return true;
}
ll cal() {
ll s = 0, e = mx - mn;
while (s < e) {
ll mid = (s + e) / 2;
if (chk(mid)) {
e = mid;
} else {
s = mid + 1;
}
}
return s;
}
int main() {
fastio();
cin >> h >> w;
v.resize(h, vector<ll>(w));
for (ll i = 0; i < h; i++) for (ll j = 0; j < w; j++) {
cin >> v[i][j];
mx = max(v[i][j], mx);
mn = min(v[i][j], mn);
}
ans = min(ans, cal());
reverse(v.begin(), v.end());
ans = min(ans, cal());
for (auto& x : v) {
reverse(x.begin(), x.end());
}
ans = min(ans, cal());
reverse(v.begin(), v.end());
ans = min(ans, cal());
cout << ans << '\n';
return 0;
}
