#include<stdio.h>
int i,j,k,m,n,s1,s2,st,v[10000][10000];
int main (){
FILE *f=fopen("flip.in","r");
FILE *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,"%d",&v[i][j]);

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

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

fprintf(g,"%d",st);
	 
fclose(f);
fclose(g);
return 0;
}