#include <fstream>
using namespace std;
int main()
{
	int a[20][20],a2,b,i,j,s;
	FILE*fin=fopen("filip.in","r");
	FILE*fout=fopen("filip.out","w");
	
	fscanf(fin,"%d%d",&a2,&b);
	for (i=0;i<a2;i++)
	{
		for (j=0;j<b;j++)
		{
			fscanf(fin,"%d",&a[i][j]);
		}
	}
	
	//for (i=0;i<a2;i++)
	//{
	//	for (j=0;j<b;j++)
	//	{
	//		fprintf(fout,"%d ",a[i][j]);
	//	}
	//	fprintf(fout,"\n");
	//}
	//fprintf(fout,"\n");
	
	s=0;
	for (i=0;i<a2;i++)
	{
		s=0;
		for (j=0;j<b;j++)
		{
			s=s+a[i][j];
		}
		if (s<0)
		{
			for (j=0;j<b;j++)
			{
				a[i][j]=a[i][j]*(-1);
			}
		}
	}
	
	
	s=0;
	for (i=0;i<b;i++)
	{
		s=0;
		for (j=0;j<a2;j++)
		{
			s=s+a[j][i];
		}
		if (s<0)
		{
			for (j=0;j<a2;j++)
			{
				a[j][i]=a[j][i]*(-1);
			}
		}
	}
	
	s=0;
	for (i=0;i<a2;i++)
	{
		for (j=0;j<b;j++)
		{
			s=s+a[i][j];
		}
	}
	
	
	fprintf(fout,"%d",s);
}