#include<stdio.h>
#include<math.h>
int main() {
long a[5][3];
int i,j,n,m,s=0,s1,s2;
FILE *f;
f=fopen("flip.in","r");
fscanf(f,"%d %d",&n,&m);
for (i=0;i<n;i++)
	for (j=0;j<m;j++)
	         fscanf(f,"%ld",&a[i][j]);
for (i=0;i<n;i++)
	{
	s1=s2=0;
	for (j=0;j<m;j++)
		if (a[i][j]<0) s1+=abs(a[i][j]);
			else s2+=a[i][j];
	if (s1>s2) for (j=0;j<m;j++)
			a[i][j]=-a[i][j];
	}
for (j=0;j<m;j++)
	{
	s1=s2=0;
	for (i=0;i<n;i++)
		if (a[i][j]<0) s1+=abs(a[i][j]);
			else s2+=a[i][j];
	if (s1>s2) for (i=0;i<n;i++)
			a[i][j]=-a[i][j];
	}
for (i=0;i<n;i++)
	for (j=0;j<m;j++) s+=a[i][j];
fclose(f);
f=fopen("flip.out","w");
fprintf(f,"%d",s);
printf("\n");
return 0;
}