#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
#define lld long double
int h, w, mn = 1e9, mx = 0;
vector<vector<int>> grid, kt;
void obrot() {
vector<vector<int>> nowe(w, vector<int>(h));
for (int i = 0; i < h; i++) {
for (int j = 0; j < w; j++) {
nowe[j][h - i - 1] = grid[i][j];
}
}
swap(grid, nowe);
swap(h, w);
}
bool solve(int x) {
kt.clear();
kt.resize(h, vector<int>(w, 0));
int pop = 0, kon;
for (int j = w - 1; j >= 0; j--) {
kon = h + 1;
for (int i = h - 1; i >= 0; i--) {
if (mx - grid[i][j] > x or i < pop) break;
kt[i][j] = 1;
kon = i;
}
pop = kon;
}
int mx0 = 0, mn0 = 1e9, mx1 = 0, mn1 = 1e9, l;
for (int i = 0; i < h; i++) {
for (int j = 0; j < w; j++) {
l = grid[i][j];
if (kt[i][j] == 0) {
mx0 = max(mx0, l);
mn0 = min(mn0, l);
}
else {
mx1 = max(mx1, l);
mn1 = min(mn1, l);
}
}
}
if (mx0 - mn0 <= x and mx1 - mn1 <= x) return 1;
return 0;
}
bool czy(int x) {
if (x == mx - mn) return 1;
bool ok = 0;
for (int i = 0; i < 4; i++) {
if (solve(x)) ok = 1;
obrot();
}
if (ok) return 1;
return 0;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int x;
cin >> h >> w;
grid.resize(h, vector<int>(w));
for (int i = 0; i < h; i++) {
for (int j = 0; j < w; j++) {
cin >> x;
grid[i][j] = x;
mx = max(mx, x);
mn = min(mn, x);
}
}
int pocz = 0, kon = mx - mn, sr;
while (pocz < kon) {
sr = (pocz + kon) / 2;
if (czy(sr)) kon = sr;
else pocz = sr + 1;
}
cout << pocz;
}
