#include <bits/stdc++.h>
using namespace std;
const int NAX_N = 2020;
int n, m;
int a[NAX_N][NAX_N];
int mn_r, mn_c;
bool check0(int d) {
int prev = m;
int mn = 1e9, mx = -1e9;
for (int r = 0; r < n; r++) {
int c = 0;
while (c < prev && a[r][c] <= a[mn_r][mn_c] + d)
c++;
if (r <= mn_r && c <= mn_c)
return false;
prev = c;
while (c < m) {
mn = min(mn, a[r][c]);
mx = max(mx, a[r][c]);
c++;
}
}
return mn + d >= mx;
}
bool check1(int d) {
int prev = -1;
int mn = 1e9, mx = -1e9;
for (int r = n - 1; r >= 0; r--) {
int c = m - 1;
while (c > prev && a[r][c] <= a[mn_r][mn_c] + d)
c--;
if (r >= mn_r && c >= mn_c)
return false;
prev = c;
while (c >= 0) {
mn = min(mn, a[r][c]);
mx = max(mx, a[r][c]);
c--;
}
}
return mn + d >= mx;
}
bool check2(int d) {
int prev = m;
int mn = 1e9, mx = -1e9;
for (int r = n - 1; r >= 0; r--) {
int c = 0;
while (c < prev && a[r][c] <= a[mn_r][mn_c] + d)
c++;
if (r >= mn_r && c <= mn_c)
return false;
prev = c;
while (c < m) {
mn = min(mn, a[r][c]);
mx = max(mx, a[r][c]);
c++;
}
}
return mn + d >= mx;
}
bool check3(int d) {
int prev = -1;
int mn = 1e9, mx = -1e9;
for (int r = 0; r < n; r++) {
int c = m - 1;
while (c > prev && a[r][c] <= a[mn_r][mn_c] + d)
c--;
if (r <= mn_r && c >= mn_c)
return false;
prev = c;
while (c >= 0) {
mn = min(mn, a[r][c]);
mx = max(mx, a[r][c]);
c--;
}
}
return mn + d >= mx;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> m;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++) {
cin >> a[i][j];
if (a[i][j] < a[mn_r][mn_c]) {
mn_r = i;
mn_c = j;
}
}
int l = -1, r = 1e9;
while (r - l > 1) {
int m = (l + r) / 2;
if (check0(m) || check1(m)
|| check2(m) || check3(m))
r = m;
else
l = m;
}
cout << r;
}
