//16.02.2007
#include<stdio.h>
int m,n;
long a[17][17];

void cit()
{
	int i,j;
	FILE *f=fopen("flip.in", "r");
	fscanf(f, "%d", &n);
	fscanf(f, "%d", &m);
	for(i=1; i<=n; i++)
		for(j=1; j<=m; j++)
			fscanf(f, "%ld", &a[i][j]);
	fclose(f);
}


void rez()
{
long s1, s2;
int i,j;
//pe linii
for(i=1; i<=n; i++)
	{
	s1=0; s2=0;
	for(j=1; j<=m; j++)
		{s1+=a[i][j];  s2=s2+(a[i][j]*(-1));}
	if(s2>s1)
		{for(j=1; j<=m; j++) a[i][j]=a[i][j]*(-1);}
	}

//pe coloane
for(j=1; j<=m; j++)
	{
	s1=0; s2=0;
	for(i=1; i<=n; i++)
		{s1+=a[i][j]; s2=s1+(a[i][j]*(-1));}
	if(s2>s1)
		{for(i=1; i<=n; i++) a[i][j]=a[i][j]*(-1);}
	}

}

int main()
{

cit();


FILE *g=fopen("flip.out", "w");
int i,j;
long s=0;
for(i=1; i<=n; i++)
	for(j=1; j<=n; j++)
		s+=a[i][j];	
printf(g, "%d", s);
fclose(g);
return 0;
}