#include <iostream.h>
#include <fstream.h>
ifstream fin("flip.in");
ofstream fout("flip.out");
int main()
{
	int n,m,i,j,s=0,k=1;
	long a[16][16];
	fin>>n>>m;
	for (i=1;i<=n;i++)
		for (j=1;j<=m;j++)
			fin>>a[i][j];
	while (k==1)
	{
		k=0;
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++)
			s=s+a[i][j];
		if (s<0)
			{
				for (j=1;j<=m;j++) a[i][j]=-1*a[i][j];
				k=1;
		}
		s=0;
	}
	for (j=1;j<=m;j++)
	{
		for (i=1;i<=n;i++)
			s=s+a[i][j];
		if (s<0) 
			{
				for (i=1;i<=n;i++) a[i][j]=-1*a[i][j];
				k=1;
		}
		s=0;
	}
	}
	for (i=1;i<=n;i++)
		for (j=1;j<=m;j++)
			s=s+a[i][j];
	fout<<s;
	return 0;
	fout.close();
}