#include <fstream.h>
ifstream cin("flip.in");
ofstream cout("flip.out");

main()
{
	int i, j, Smax = 0 ;
	int n , m;
	cin >> n >> m;
	int c[n][m];
	
	//initializarea sumelor (pe rand si pe coloana)
	int Sc[m];
	int Sr[n];
	for (i=1; i<=n ; i++){
		Sr[i] = 0;}
	for (j=1; j<=m ; i++){
		Sc[j] = 0;}

    
    //citirea casutelor 
	for (i=1 ; i<=n ; i++){
		for (j=1 ; j<=m ; j++){
			cin >> c[i][j];
		}
	}

	//calculul sumelor (pe randuri / coloane) 
	for (j=1 ; j<=m; j++) {
		for (i=1 ; i<=n ; i++){
			Sc[j] = Sc[j] + c[i][j];
		}
	}
	for (i=1 ; i<=n; i++) {
		for (j=1 ; j<=m ; j++){
			Sr[i] = Sr[i] + c[i][j];
		}
	}
	
	
	//schimburile de stare necesare
	for (j=1 ; j<=m; j++) {
		if (Sc[j] < 0){
			for (i=1 ; i<=n ; i++){
				c[i][j] = c[i][j]*(-1);}
		}
	}
	for (i=1 ; i<=n; i++) {
		if (Sr[i] < 0){
			for (j=1 ; j<=m ; j++){
				c[i][j] = c[i][j]*(-1);}			
	}


	//calcularea afisarea sumei maxime
	for (i=1 ; i<=n ; i++){
		for (j=1 ; j<=m ; j++){
			Smax = Smax + c[i][j];			
		}
	}
	cout << Smax;
}