#include<fstream.h>
#include<math.h>
int main()
{long a[16][16],n,m,i,s=0,sp,sn,j;
ifstream f("flip.in");
ofstream g("flip.out");
f>>n; f>>m;
for (i=1; i<=n; i++)
	{sn=0; sp=0;
	for (j=1; j<=m; j++)
		{f>>a[i][j];
		if (a[i][j]>0) sp++;
		else sn++;}
	if (sn>sp) for (j=1; j<=m; j++) a[i][j]=-a[i][j];}
for (j=1; j<=m; j++)
	{sp=0; sn=0;
	for (i=1; i<=n; i++)
		if (a[i][j]> 0) sp++;
		else sn++;
	if (sn>sp) for (i=1; i<=n; i++) a[i][j]=-a[i][j];}
for (i=1; i<=n; i++)
	for (j=1; j<=m; j++)
		s=s+a[i][j];
g<<s;
f.close();
g.close();return 0;}