#include<fstream.h>
ifstream f("flip.in");
ofstream g("flip.out");

int main ()
{
	long a[20][20],m,n,i,j,ok,s1,s2;
	f>>m>>n;
	for (i=1; i<=m; i++)
		for (j=1; j<=n; j++)
			f>>a[i][j];
	ok=1;
	while (ok==1)
	{
		ok=0;
		for (i=1; i<=m; i++)
		{
			s1=0; s2=0;
			for (j=1; j<=n; j++)
			{
				s1+=a[i][j];
				s2+=-a[i][j];
			}
			if (s1<s2) 
				{ for (j=1; j<=n; j++) a[i][j]=-a[i][j]; ok=1; }
		}
		for (j=1; j<=n; j++)
		{
			s1=0; s2=0;
			for (i=1; i<=m; i++)
			{
				s1+=a[i][j];
				s2+=-a[i][j];
			}
			if (s1<s2)
				{ for (i=1; i<=m; i++) a[i][j]=-a[i][j]; ok=1; }
		}
	}
	s1=0;
	for (i=1; i<=m; i++)
		for (j=1; j<=n; j++)
			s1+=a[i][j];
	g<<s1;
	return 0;
}