#include <iostream>
#include <fstream>

using namespace std;

ifstream cin ("flip.in");
ofstream cout ("flip.out");

int main()
{ 
	int a[17][17],n,m,i,j,s;
	//citire matrice
	cin>>n>>" ">>m;
	for (i=1;i<=m;i++)
	{
	for (j=1;j<=n;j++)
		cin>>a[i][j];}
	//verificare linie
	for (i=1;i<=m;i++)
	{	s=0;
		for (j=1j<=n;j++)
		s=s+a[i][j];
		if (s<0)
		a[i][j]=a[i][j]*(-1);
	}
	//verificare linie
	for (j=1;j<=n;j++)
	{	s=0;
		for (i=1;i<=m;i++)
		s=s+a[i][j];
		if (s<0)
		a[i][j]=a[i][j]*(-1);
	}
	//suma maxima
	s=0;
	for (i=1;i<=m;i++)
	{for (j=1;j<=n;j++)
	s=s+a[i][j];}
	cout<<s;
	return 0;
}
}