#include <iostream>
#include <fstream>

using namespace std;

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

	int N, M;

	fin >> N >> M;

	int v[10][16];

	for (int i = 0; i < N; i++) {
		for (int j = 0; j < M; j++)
			fin >> v[i][j];
	}

	int sum;

	for (int i = 0; i < N; i++) {
		sum = 0;

		for (int j = 0; j < M; j++)
			sum += v[i][j];

		if (sum < 0) {
			for (int j = 0; j < M; j++)
				v[i][j] *= -1;
		}
	}

	for (int i = 0; i < M; i++) {
		sum = 0;

		for (int j = 0; j < N; j++)
			sum += v[j][i];

		if (sum < 0) {
			for (int j = 0; j < N; j++)
				v[j][i] *= -1;;
		}
	}

	sum = 0;

	for (int i = 0; i < N; i++) {
		for (int j = 0; j < M; j++)
			sum += v[i][j];
	}

	fout << sum;

	fout.close();

	return 0;
}