#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <unordered_map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
#define ll long long
#define ld long double
#define inf (ll)(2*1e18)
//#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define pb push_back
#define endl "\n"
using namespace std;
bool check(ll x, ll n, ll m, vector<vector<ll>>& val, vector<vector<ll>>& a, vector<vector<ll>>& b, vector<vector<ll>>& c, vector<vector<ll>>& d){
ll mi=inf, k=a[n][m], A=0, B=0, C=0, D=0;
for(int i=1;i<=n;++i){
for(int j=1;j<=m;++j){
if(val[i][j] + x < k){
mi = min(mi, val[i][j]);
A = max(A, a[i][j]);
B = max(B, b[i][j]);
C = max(C, c[i][j]);
D = max(D, d[i][j]);
}
}
}
if(mi + x < min({A, B, C, D})){
return true;
}
return false;
}
void solve(){
ll n, m, i, j, l=0, r=1e9, mid;
cin>>n>>m;
vector<vector<ll>> val(n+2, vector<ll>(m+2));
vector<vector<ll>> a(n+2, vector<ll>(m+2));
vector<vector<ll>> b(n+2, vector<ll>(m+2));
vector<vector<ll>> c(n+2, vector<ll>(m+2));
vector<vector<ll>> d(n+2, vector<ll>(m+2));
for(i=1;i<=n;++i){
for(j=1;j<=m;++j){
cin>>val[i][j];
}
}
for(i=1;i<=n;++i){
for(j=1;j<=m;++j){
a[i][j] = max({val[i][j], a[i-1][j], a[i][j-1]});
}
for(j=m;j>=1;--j){
b[i][j] = max({val[i][j], b[i-1][j], b[i][j+1]});
}
}
for(i=n;i>=1;--i){
for(j=1;j<=m;++j){
c[i][j] = max({val[i][j], c[i+1][j], c[i][j-1]});
}
for(j=m;j>=1;--j){
d[i][j] = max({val[i][j], d[i+1][j], d[i][j+1]});
}
}
while(r - l > 1){
mid = (l+r)/2;
if(check(mid, n, m, val, a, b, c, d)){
l = mid;
}else{
r = mid;
}
}
cout<<r<<endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
srand(time(nullptr));
ll t=1;
// cin>>t;
for(;t>0;--t){
solve();
}
return 0;
}
