#include<fstream.h>
main()
{
ifstream in("flip.in");
ofstream o("flip.out");
int m,n,i,j;
long a[20][20], s1, s2;
in>>n>>m;
for(i=1;i<=n;i++)
{	for(j=1,s1=0;j<=m;j++)
	{	in>>a[i][j];
		s1+=a[i][j];
	}
	if(s1<0)
		for(j=1;j<=m;j++)
			a[i][j]=0-a[i][j];
}
for(j=1;j<=m;j++)
{	for(i=1,s1=0;i<=n;i++)
		s1+=a[i][j];
	if(s1<0)
		for(i=1;i<=n;i++)
			a[i][j]=0-a[i][j];
}
for(i=1,s1=0;i<=n;i++)
	for(j=1;j<=m;j++)
		s1+=a[i][j];
o<<s1;
in.close();
o.close();
return 0;
}