#include<fstream.h>
#include<iostream.h>
int a[17][17],n,m,max;
void linie(int i)
{
for(int j=1;j<=m;j++)
	a[i][j]*=-1;
}
void coloana(int j)
{
for(int i=1;i<=n;i++)
	a[i][j]*=-1;
}
void chestie(int i, int j, int &s)
{

if(s>max)max=s;
for(;i<=n;i++)
	for(;j<=m;j++)
	if(a[i][j]>=0)s+=a[i][j];
	else{
		linie(i);chestie(i+1,j+1,s);
		coloana(j);chestie(i+1,j+1,s);
		linie(i);coloana(j);chestie(i+1,j+1,s);
		}

}
int main ()
{
int i,j,s=0;
ifstream f("flip.in");
ofstream g("flip.out");
f>>n>>m;
for(i=1;i<=n;i++)
	for(j=1;j<=m;j++)
	f>>a[i][j];
	chestie(1,1,s);
g<<max*2<<"\n";
	return 0;
}