#include <bits/stdc++.h>
using namespace std;
int h, w, mn, ans = 1e9+1;
vector<vector<int>> arr;
bool check(int val) {
int mn2=1e9+1, mx2=0, bound=w+1;
for(int i=0; i<h; i++) {
for(int j=0; j<w; j++) {
if(arr[i][j] > mn+val) {
bound = min(bound, j);
}
if(j >= bound) {
mn2 = min(mn2, arr[i][j]);
mx2 = max(mx2, arr[i][j]);
}
}
}
if(mx2-mn2 <= val) return true;
return false;
}
int find() {
int l=-1, r=1e9+1;
while(l < r) {
int mid = l+(r-l)/2;
if(check(mid)) {
r = mid;
} else {
l = mid+1;
}
}
return l;
}
signed main() {
cin >> h >> w;
arr.assign(h, vector<int>(w, 0));
for(int i=0; i<h; i++) {
for(int j=0; j<w; j++) {
cin >> arr[i][j];
}
}
mn = arr[0][0];
for(int i=0; i<h; i++) {
for(int j=0; j<w; j++) {
mn = min(mn, arr[i][j]);
}
}
ans = min(ans, find());
reverse(arr.begin(), arr.end());
ans = min(ans, find());
for(int i=0; i<h; i++) {
reverse(arr[i].begin(), arr[i].end());
}
ans = min(ans, find());
reverse(arr.begin(), arr.end());
ans = min(ans, find());
cout << ans;
return 0;
}
