// JOI chứa min, IOI chứa max
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const int N = 2000 + 3, inf = 1e9 + 7;
int h, w;
int a[N][N], mi = inf, ma;
bool check1(int diff) { // trái trên
for (int i = 1, p(w); i <= h; ++i) {
for (int j = p; j; --j)
if (a[i][j] - mi > diff) p = min(p, j - 1); // [1..p] [p+1..w]
for (int j = p + 1; j <= w; ++j)
if (ma - a[i][j] > diff) return false;
}
return true;
}
bool check2(int diff) { // trái dưới
for (int i = h, p(w); i; --i) {
for (int j = p; j; --j)
if (a[i][j] - mi > diff) p = min(p, j - 1); // [1..p] [p+1..w]
for (int j = p + 1; j <= w; ++j)
if (ma - a[i][j] > diff) return false;
}
return true;
}
bool check3(int diff) { // phải trên
for (int i = 1, p(w); i <= h; ++i) {
for (int j = p; j; --j)
if (ma - a[i][j] > diff) p = min(p, j - 1); // [1..p] [p+1..w]
for (int j = p + 1; j <= w; ++j)
if (a[i][j] - mi > diff) return false;
}
return true;
}
bool check4(int diff) { // phải dưới
for (int i = h, p(w); i; --i) {
for (int j = p; j; --j)
if (ma - a[i][j] > diff) p = min(p, j - 1); // [1..p] [p+1..w]
for (int j = p + 1; j <= w; ++j)
if (a[i][j] - mi > diff) return false;
}
return true;
}
int main() {
cin.tie(NULL)->sync_with_stdio(false);
cin >> h >> w;
for (int i = 1; i <= h; ++i)
for (int j = 1; j <= w; ++j) {
cin >> a[i][j];
mi = min(mi, a[i][j]);
ma = max(ma, a[i][j]);
}
int lo(0), hi(ma - mi - 1), m;
while (lo <= hi) {
m = (lo + hi) >> 1;
if (check1(m) || check2(m) || check3(m) || check4(m))
hi = m - 1;
else lo = m + 1;
}
cout << hi + 1 << '\n';
}
/** /\_/\
* (= ._.)
* / >0 \>1
**/
