#include <bits/stdc++.h>
using namespace std;
#define print(l) for(auto i:l) cout<<i<<" ";cout<<endl;
#define input(t,l,n) vector<t>l(n);for(int i = 0;i<n;i++)cin>>l[i];
#define int long long
#define pb push_back
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define all(l) l.begin(),l.end()
#define pii pair<int,int>
#define fi first
#define se second
const int M = 1e9+7;
const int inf = 1e18;
int bp(int x, int y, int p){
int res = 1;
x = x % p;
while (y > 0) {
if (y & 1)
res = (res * x) % p;
y = y >> 1;
x = (x * x) % p;
}
return res;
}
int MI(int n, int p){
return bp(n, p - 2, p);
}
int mul(int x,int y, int p){
return x * 1ull * y % p;
}
int di(int x,int y, int p){
return mul(x, MI(y, p), p);
}
int n , m , k , q;
void solve(int testcase_number){
cin>>n>>m;
// vector<vector<vector<int>>>dp(n+1,vecor<int>(m+1,vector<int>(3,0)));
int dp[n+1][m+1][3] = {};
for(int i =0;i<=n;i++){
dp[i][0][0] = 0;
dp[i][0][1] = inf;
dp[i][0][2] = -inf;
}
for(int i =0;i<=m;i++){
dp[0][i][0] = 0;
dp[0][i][1] = inf;
dp[0][i][2] = -inf;
}
int mat[n+1][m+1];
for(int i = 1;i<=n;i++){
for(int j = 1;j<=m;j++){
cin>>mat[i][j];
}
}
int ans = 0;
for(int i = 1;i<=n;i++){
for(int j = 1;j<=m;j++){
vector<int>p1(3,0);
p1[0] = dp[i-1][j][0];
p1[1] = dp[i-1][j][1];
p1[2] = dp[i-1][j][2];
vector<int>p2(3,0);
p2[0] = dp[i][j-1][0];
p2[1] = dp[i][j-1][1];
p2[2] = dp[i][j-1][2];
p2[1] = min(p2[1],mat[i][j]);
p2[2] = max(p2[2],mat[i][j]);
p1[1] = min(p1[1],mat[i][j]);
p1[2] = max(p1[2],mat[i][j]);
// cout<<min(p1[]mat[i][j]<<endl;
// print(p1);
// print(p2);
if(p2[2]-p2[1]-p2[0]-1 > p1[2]-p1[1]-p1[0]-1){
dp[i][j][0] = p2[0]+1;
dp[i][j][1] = p2[1];
dp[i][j][2] = p2[2];
}
else if(p2[2]-p2[1]-p2[0]-1 < p1[2]-p1[1]-p1[0]-1){
dp[i][j][0] = p1[0]+1;
dp[i][j][1] = p1[1];
dp[i][j][2] = p1[2];
}
else{
if(p2[0] <= p1[0]){
dp[i][j][0] = p2[0]+1;
dp[i][j][1] = p2[1];
dp[i][j][2] = p2[2];
}
else{
dp[i][j][0] = p1[0]+1;
dp[i][j][1] = p1[1];
dp[i][j][2] = p1[2];
}
}
ans = max(ans,dp[i][j][2]-dp[i][j][1]-dp[i][j][0]);
}
}
cout<<ans<<endl;
}
signed main(){
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);
cout << fixed<<setprecision(9);
int t = 1;
// cin>>t;
for(int i = 1;i<=t;i++){
solve(i);
}
}
