#include<stdio.h>
#include<conio.h>
#include<iostream.h>
#include<fstream.h>
#include<string.h>
 int n,j,a[20][20],i,m;
  main()


{ clrscr();


 FILE *f1=fopen("flip.in","r");

 fscanf(f1,"%d%d",&n,&m);

 for (i=1;i<=n;i++)
  for (j=1;j<=m;j++)
  fscanf(f1,"%d",&a[i][j]);
    int s1=0, s2=0;

 for (i=1;i<=n;i++)
    {
     if (s2<s1) { for (j=1;j<=m;j++) a[i-1][j]*=-1; }
		  s1=0;s2=0;

    for (j=1;j<=m;j++)
     { if (a[i][j]<0) { s1+=a[i][j];} else {s2+=a[i][j];}

      s1*=-1;	  }

     }


   s1=0, s2=0;
 for (j=1;j<=m;j++)
    {
     if (s2<s1) { for (i=1;i<=n;i++) a[i][j-1]*=-1; }
		  s1=0;s2=0;

    for (i=1;i<=n;i++)
     { if (a[i][j]<0) { s1+=a[i][j]; } else {s2+=a[i][j];}

      s1*=-1;	  }

     }



     int s=0;
for (i=1;i<=n;i++)

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


	       FILE *f2=fopen("flip.out","w");
	 fprintf(f2,"%d", s);
	 flcose(f1);
	 fclose(f2);
getche();
}