#include <iostream>
#include <fstream>

using namespace std;

ifstream f("flip.in");
ofstream g("flip.out");
int vect[10000][10000];
int a, b;
void	citire() {
	
	int	value;

	f >> a >> b;
	for (int i = 0;i < a; ++i){
		for (int j = 0; j < b; ++j) {
			f >> value;
			vect[i][j] = value;
		}
	}
}

void	Inv_Col() {
	int sum = 0;
	for (int i = 0; i < a; ++i) {
		for (int j = 0; j < b; ++j) {
			sum = sum + vect[i][j];
		}
		if (sum < 0)
			for (int j = 0; j < b; ++j)
				vect[i][j] *= (-1);
		sum = 0;
	}
}

void	Inv_Row() {
	int sum = 0;
	for (int j = 0; j < b; ++j)	{
		for (int i = 0; i < a; ++i) 
			sum = sum + vect[i][j];

		if (sum < 0)
			for (int k = 0; k < a; ++k)
				vect[k][j] *= (-1);
		sum = 0;
	}
}

void Sum() {
	int sum = 0;
	for (int i = 0; i < a; ++i)
		for (int j = 0; j < b; ++j)
			sum = sum + vect[i][j];
	g << sum << endl;
}

int		main(){
	citire();
	Inv_Col();
	Inv_Row();
	Sum();
    return 0;
}