#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#define pb emplace_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
using namespace std;
const int N = int(2e3) + 3;
const int inf = int(1e9) + 3;
int n, m, a[N][N], low, mid, high, lim, mn, mx, res, Mx, Mn, h;
bool divided;
bool Check() {
lim = mn + mid;
if(a[0][0] > lim && a[0][m - 1] > lim) return 0;
Mx = 0, Mn = inf, h = n;
for(int j = 0; j < m; ++j) {
divided = 0;
if(a[0][j] > lim) h = 0, divided = 1;
for(int i = 0; i < n; ++i) {
if(a[i][j] <= lim && i < h && !divided) continue;
if(!divided) divided = 1, h = min(h, i);
Mx = max(Mx, a[i][j]), Mn = min(Mn, a[i][j]);
}
}
if(Mx - Mn <= mid) return 1;
h = n, Mx = 0, Mn = inf;
for(int j = m - 1; j >= 0; --j) {
divided = 0;
if(a[0][j] > lim) h = 0, divided = 1;
for(int i = 0; i < n; ++i) {
if(a[i][j] <= lim && i < h && !divided) continue;
if(!divided) divided = 1, h = min(h, i);
Mx = max(Mx, a[i][j]), Mn = min(Mn, a[i][j]);
}
}
return Mx - Mn <= mid;
}
void Solve() {
mid = res - 1;
if(!Check()) return;
low = 0, high = res - 1;
while(low <= high) {
mid = (low + high) >> 1;
if(Check()) high = mid - 1;
else low = mid + 1;
}
res = min(res, low);
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
if(fopen("test.inp", "r")) {
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
}
cin >> n >> m; mn = inf, mx = 0;
for(int i = 0; i < n; ++i) {
for(int j = 0; j < m; ++j) {
cin >> a[i][j];
mn = min(mn, a[i][j]);
mx = max(mx, a[i][j]);
}
}
res = mx - mn;
Solve();
for(int j = 0; j < m; ++j) {
for(int i = 0; n - 1 - i > i; ++i) {
swap(a[i][j], a[n - 1 - i][j]);
}
}
Solve();
cout << res;
}
