#include <fstream>

using std::ifstream; using std::ofstream;

const unsigned int MAX_MAT_SIZE=16;

struct Mat {
	long mat[MAX_MAT_SIZE][MAX_MAT_SIZE];
	unsigned int size_l,size_c;
};

bool invColoane (Mat &M);
bool invLinii (Mat &M);
long long Suma (const Mat &M);


int main (void)
{
	ifstream f_in("flip.in");
	ofstream f_out("flip.out");
	if (!f_in.good() || !f_out.good()) {
		f_in.close(); f_out.close();
		return -1;
	}
	Mat M;
	f_in>>M.size_l>>M.size_c;
	for (unsigned int l=0; l<M.size_l; l++)
		for (unsigned int c=0; c<M.size_c; c++)
			f_in>>M.mat[l][c];

	bool coloana=true,a1=true,a2=true;
	while (a1||a2) {
		if (coloana) a1=invColoane(M);
		else a2=invLinii(M);
		coloana=!coloana;
	}
	f_out << Suma(M) << '\n';
    return 0;
}

//true daca a fost inversata vreo coloana
bool invColoane (Mat &M)
{
	bool inv=false;
	long S;
	unsigned int l;
	for (unsigned int c=0; c<M.size_c; c++) {
		S=0;
		for (l=0; l<M.size_l; l++)
			S += M.mat[l][c];
		if (S<0) {
			inv=true;
			for (l=0; l<M.size_l; l++)
				M.mat[l][c] = ~M.mat[l][c]+1;
		}
		
	}
	return inv;
}

bool invLinii (Mat &M)
{
	bool inv=false;
	long S;
	unsigned int c;
	for (unsigned int l=0; l<M.size_l; l++) {
		S=0;
		for (c=0; c<M.size_c; c++)
			S += M.mat[l][c];
		if (S<0) {
			inv=true;
			for (c=0; c<M.size_c; c++)
				M.mat[l][c] = ~M.mat[l][c]+1;
		}
		
	}
	return inv;
}

long long Suma (const Mat &M)
{
	long long ret=0;
	for (unsigned int c=0; c<M.size_c; c++)
		for (unsigned int l=0; l<M.size_l; l++)
			ret += M.mat[l][c];
	return ret;
}