#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define ll long long
#define hash deep_dark_fantasy
#define inf 1e9
using namespace std;
inline int read(){
int re=0,flag=1;char ch=getchar();
while(ch>'9'||ch<'0'){
if(ch=='-') flag=-1;
ch=getchar();
}
while(ch>='0'&&ch<='9') re=(re<<1)+(re<<3)+ch-'0',ch=getchar();
return reflag;
}
int n,m,x[150][150],cur,pre,ex,ey;
int st[2][300010];ll ans[2][300010],re;
int tot[2],bit[20],state[300010],st_tot,hash=300000;
struct edge{
int to,next;
}a[300010];
void insert(int sta,ll val){
int p=sta%hash,i;
for(i=state[p];i;i=a[i].next){
if(st[cur][a[i].to]==sta){
ans[cur][a[i].to]=max(ans[cur][a[i].to],val);return;
}
}
tot[cur];
a[st_tot].to=tot[cur];
a[st_tot].next=state[p];
state[p]=st_tot;st[cur][tot[cur]]=sta;ans[cur][tot[cur]]=val;
}
void dp(){
int i,j,k,l,now,down,right;ll val;re=-inf;
cur=0;tot[cur]=1;ans[cur][1]=0;st[cur][1]=0;
for(i=1;i<=n;i){
for(j=1;j<=tot[cur];j) st[cur][j]<<=2;
for(j=1;j<=m;j++){
pre=cur;cur^=1;tot[cur]=0;st_tot=0;memset(state,0,sizeof(state));
for(k=1;k<=tot[pre];k++){
now=st[pre][k];val=ans[pre][k];
right=(now>>bit[j-1])%4;down=(now>>bit[j])%4;
if(!down&&!right){
insert(now,val);
if(j!=m)
insert(now+(1<<bit[j-1])+((1<<bit[j])<<1),val+x[i][j]);
}
if(down&&!right){
insert(now-down(1<<bit[j])+down*(1<<bit[j-1]),val+x[i][j]);
if(j!=m)insert(now,val+x[i][j]);
}
if(right&&!down){
insert(now,val+x[i][j]);
if(j!=m)
insert(now+right*(1<<bit[j])-right*(1<<bit[j-1]),val+x[i][j]);
}
if(right1&&down1){
int cnt=1;
for(l=j+1;l<=m;l++){
if((now>>bit[l])%41) cnt++;
if((now>>bit[l])%42) cnt--;
if(!cnt){
insert(now-(1<<bit[l])-(1<<bit[j])-(1<<bit[j-1]),val+x[i][j]);
break;
}
}
}
if(right2&&down2){
int cnt=1;
for(l=j-2;l>=0;l--){
if((now>>bit[l])%41) cnt--;
if((now>>bit[l])%42) cnt++;
if(!cnt){
insert(now+(1<<bit[l])-((1<<bit[j])<<1)-((1<<bit[j-1])<<1),val+x[i][j]);
break;
}
}
}
if(right2&&down1){
insert(now-((1<<bit[j-1])<<1)-(1<<bit[j]),val+x[i][j]);
}
if(right1&&down2){
if((now==(1<<bit[j-1])+((1<<bit[j])<<1))&&(val+x[i][j]>re)){
re=val+x[i][j];
}
}
}
}
}
}
int main(){
int i,j;
n=read();m=read();
for(i=1;i<=10;i++) bit[i]=(i<<1);
for(i=1;i<=n;i++) for(j=1;j<=m;j++) x[i][j]=read();
dp();
printf("%lld",re);
}
