#include<stdio.h>
int m,n,i,j;
long a[16][16];
long st,stt,sp,sn;
FILE *f,*g;
int main()
{f=fopen("flip.in","r");
g=fopen("flip.out","w");
fscanf(f,"%d%d",&n,&m);
for (i=1;i<=n;i++)
for (j=1;j<=m;j++)
fscanf(f,"%ld",&a[i][j]);
for (i=1;i<=n;i++)
{sp=0;sn=0;
for (j=1;j<=m;j++)
if (a[i][j]>0) sp=sp+a[i][j];
	else   sn=sn-a[i][j];
if (sp<sn)
{for (j=1;j<=m;j++)
a[i][j]=-a[i][j];} }
for (j=1;j<=m;j++)
{sp=0;sn=0;
for (i=1;i<=m;i++)
if (a[i][j]>0) sp=sp+a[i][j];
	else   sn=sn-a[i][j];
if (sp<sn)
{for (i=1;i<=n;i++)
a[i][j]=-a[i][j];}}
for (i=1;i<=n;i++)
for (j=1;j<=m;j++)
st=st+a[i][j];
fprintf(g,"%ld",st);
fclose(f);
fclose(g);
return 0;}