#include <stdio.h>
FILE* f;
FILE* s;
int m,n;
int i;
int l,c;
long int t[100][100];
long int sn,sp;
main()
{
	f=fopen ("filip.in","r");
	s=fopen ("filip.out","w");

	fscanf (f,"%d %d\n",&n,&m);

	for (l=0;l<n;l++)
	{
		for (c=0;c<m;c++)
		{
			fscanf (f,"%ld ",&t[l][c]);
		}
		fscanf (f,"\n");
	}

	for (l=0;l<n;l++)
	{
		sn=0;
		sp=0;
		for (c=0;c<m;c++)
		{
			if (t[l][c]>=0)
				sp=sp+t[l][c];
			else
				sn=sn+t[l][c]*(-1);

		}
		if (sn>sp)
			for (i=0;i<m;i++)
				t[l][i]=t[l][i]*(-1);
	}

	for (c=0;c<m;c++)
	{
		sn=0;
		sp=0;
		for (l=0;l<n;l++)
		{
			if (t[l][c]>=0)
				sp=sp+t[l][c];
			else
				sn=sn+t[l][c]*(-1);

		}
		if (sn>sp)
			for (i=0;i<n;i++)
				t[i][c]=t[i][c]*(-1);
	}

	sp=0;
	for (l=0;l<n;l++)
		for (c=0;c<m;c++)
		{
			sp=sp+t[l][c];
		}


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

	fclose (s);
	fclose (f);
}