#include<bits/stdc++.h>
using namespace std;
vector<pair<int,pair<int,int>>> haha(0);
int bruh[2001][2001];
int n,m;
int calc() {
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
bruh[i][j] = 1;
}
}
vector<int> sm(m);
vector<int> big(m,-1);
int ans = haha[haha.size()-1].first-haha[0].first;
int br = 0,p = 0;
for(int i = 0; i < n*m; i++) {
int x = haha[i].second.first,y = haha[i].second.second;
for(int j = y; j < m; j++) {
if(big[j] >= sm[j]) {
br--;
}
if(big[j] < x) {
big[j] = x;
if(big[j] >= sm[j]) {
br++;
}
}
else {
break;
}
}
while(br > 0) {
int a = haha[p].second.first,b = haha[p].second.second;
bruh[a][b] = 0;
if(big[b] >= sm[b]) {
br--;
}
while(sm[b] < n && bruh[sm[b]][b] == 0) {
sm[b]++;
}
if(big[b] >= sm[b]) {
br++;
}
p++;
}
int c = haha[p-1].first-haha[0].first;
if(i < n*m) {
c = max(c,haha[n*m-1].first-haha[i+1].first);
}
ans = min(ans,c);
}
return ans;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m;
int a,ans = INT_MAX;
for(int i = 0; i < n; i++) {
for(int j = 0; j < m; j++) {
cin >> a;
haha.push_back({a,{i,j}});
}
}
sort(haha.begin(),haha.end());
ans = min(ans,calc());
for(int i = 0; i < n*m; i++) {
haha[i] = {haha[i].first,{n-1-haha[i].second.first,m-1-haha[i].second.second}};
}
ans = min(ans,calc());
for(int i = 0; i < n*m; i++) {
haha[i] = {haha[i].first,{n-1-haha[i].second.first,haha[i].second.second}};
}
ans = min(ans,calc());
for(int i = 0; i < n*m; i++) {
haha[i] = {haha[i].first,{n-1-haha[i].second.first,m-1-haha[i].second.second}};
}
ans = min(ans,calc());
cout << ans;
return 0;
}
