#include<stdio.h>
int main()
{int N,M,i,j;
 long a[17][17],s,S=0;
 FILE*f,*g;
 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(j=1;j<=M;j++)
	{s=0;
	 for(i=1;i<=N;i++)
		s+=a[i][j];
         if(s<0) for(i=1;i<=N;i++)
			a[i][j]=-a[i][j];}
 for(i=1;i<=N;i++)
	{s=0;
         for(j=1;j<=M;j++)
		s+=a[i][j];
         if(s<0) for(j=1;j<=M;j++)
			a[i][j]=-a[i][j];}
 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;
}