#include<cstdio>
int main ()
{
	long n,m,i,j,sl,sc,s=0,v[256][256],k;
	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++) {
		sl=0;
		for (j=1;j<=m;j++) 
			sl+=v[i][j];
		if (sl<0) 
			for (k=1;k<=m;k++)
				v[i][k]=v[i][k]*(-1);
	}
	for (j=1;j<=m;j++) {
		sc=0;
		for (i=1;i<=n;i++)
			sc+=v[i][j];
		if (sc<0) 
			for (k=1;k<=n;k++)
				v[k][j]=v[k][j]*(-1);
	}
	for(i=1;i<=n;i++)
		for (j=1;j<=m;j++)
			s+=v[i][j];
	fprintf(g,"%d",s);
	fclose(f);
	fclose(g);
	return 0;
}