#include <fstream>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");


int m,n, Suma, i, j;
long M[28][28];

int main()
{
	// citire
	fin >> n >> m;
	for ( i = 1 ; i <= n ; i++)
		for ( j = 1 ; j <= m ; j++ )
			fin >> M[i][j] ;
		
		// coloane
	for ( i = 1 ; i<=m ; i++ )
	{
		for ( j = 1 ; j <= n;  j++ )
			Suma+= M[j][i];
		if ( Suma < 0 )
			for ( j = 1 ; j <= n;  j++ ) M[j][i] = - M[j][i] ;
		Suma  =  0 ;
	}
		
	// linii
	for ( i = 1 ; i<=n ; i++ )
	{
		for ( j = 1 ; j <= m; j++ )
			Suma += M[i][j];
		if ( Suma < 0 )
			for ( j = 1 ; j <= m ; j++ ) M[i][j] = -M[i][j];
		Suma = 0;
	}
	
	
	
	Suma = 0 ;
	for ( i = 1 ; i <= n ; i++ )
		for ( j = 1 ; j <= m ; j++ )
			Suma+= M[i][j];
	
	fout << Suma << '\n' ;
	return 0;
	
}