#include <stdio.h>
#include <math.h>
#include <mem.h>


int n,m,a[20][20],i,j,b[3][20];
long po,ne;



int main()
{
FILE *fi=fopen("flip.in","r"), *fo=fopen("flip.out","w");
fscanf(fi,"%d %d",&n,&m);

setmem(a,sizeof(a),0);
setmem(b,sizeof(b),0);

for(i=1;i<=n;i++)
{ po=ne=0;

  for(j=1;j<=m;j++)
   { fscanf(fi,"%d",&a[i][j]);
    if(a[i][j]<0)ne+=a[i][j];
     else po+=a[i][j];
   }
if(abs(po)<abs(ne))b[1][i]=1;
}


for(i=1;i<=m;i++)
{ po=ne=0;
 for(j=1;j<=n;j++)
 { if(a[j][i]<0)ne+=a[j][i];
   else po+=a[j][i];
 }

if(abs(po)<abs(ne))b[2][i]=1;
}

for(i=1;i<=5;i++)
{
if(b[1][i]==1)
 {
  for(j=1;j<=m;j++)
    a[i][j]*=-1;
 }

if(b[2][i]==1)
 {
  for(j=1;j<=n;j++)
  a[j][i]*=-1;
 }

}

long s=0;

for(i=1;i<=n;i++)
 for(j=1;j<=m;j++)
   s+=a[i][j];





fprintf(fo,"%ld",s);



return 0;
}