#include <stdio.h>

void main(){
FILE *f,*g;
f=fopen("flip.in","r");
g=fopen("flip.out","w");
int n,m,j,i;
long a[17][17],e=0,d=0;
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<=m;++i)
  {
   for(j=1;j<=n;++j)
     if(a[j][i]<0) e=e-a[j][i];
	else d=d+a[j][i];
   if(e>d) for(j=1;j<=n;j++) a[j][i]=-a[j][i];
   e=0;d=0;
  }

e=0;d=0;

for(i=1;i<=n;++i)
  {
   for(j=1;j<=m;++j)
     if(a[i][j]<0) e=e-a[i][j];
	else d=d+a[i][j];
   if(e>d) for(j=1;j<=m;++j) a[i][j]=-a[i][j];
   e=0;d=0;
  }


e=0; printf("\n");

for(i=1;i<=n;i++){
 for(j=1;j<=m;j++)
   e=e+a[i][j];
}

fprintf(g,"%ld",e);

fcloseall();
}