#include<iostream.h>
#include<fstream.h>
#include<limits.h>
#define IN ifstream f("flip.in");
#define OUT ofstream g("flip.out");
#define INC f.close();
#define OUTC g.close();
int xx,yy,map[16][16];
int max=INT_MIN;
int flip[32];
int suma(){
	int sum=0,_sum=0;
	for(int y=0;y<yy;y++)
	for(int x=0;x<xx;x++)
		sum+=map[x][y]*flip[x]*flip[xx+y];
	if(sum>max)max=sum;
	if(_sum>max)max=_sum;
return sum;}
void rezolva(int i){
	if(i==xx*yy)suma();
	else{
		flip[i]=-1;
		rezolva(i+1);
		flip[i]=1;
		rezolva(i+1);}}
void citeste(){
	IN f>>yy>>xx;
	for(int y=0;y<yy;y++)
	for(int x=0;x<xx;x++)
	f>>map[x][y];INC}
int main(){
	citeste();
	rezolva(0);
	OUT g<<max;OUTC
return 0;}