#include <stdio.h>
#include <math.h>
#include <values.h>
FILE *f=fopen("flip.in","r"), *g=fopen("flip.out","w");
int main()
{
long p=1,lll,ccc,min,s=0,ss=0,n,m,i,j,a[100][100];
fscanf(f,"%ld %ld",&n,&m);
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		fscanf(f,"%ld",&a[i][j]);

while (p)
{
min=MAXLONG;
for (i=1;i<=m;i++)
{
	for (j=1;j<=n;j++)
		s+=a[j][i];
	if (min>s)
		{
		min=s;
		lll=0;
		ccc=i;
		}
	s=0;
}

for (i=1;i<=n;i++)
{
	for (j=1;j<=m;j++)
		s+=a[i][j];
	ss+=s;
	if (min>s)
		{
		min=s;
		ccc=0;
		lll=i;
		}
	s=0;
}

if (min>=0) {
		p=0;
		ccc=0;
		lll=0;
	   }
if (ccc)
	for (i=1;i<=n;i++)
		a[i][ccc]*=-1;
if (lll)
	for (i=1;i<=m;i++)
		a[lll][i]*=-1;
}
s=0;
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		s+=a[i][j];
fprintf(g,"%ld",s);
fclose(f);
fclose(g);
return 0;
}