#include<iostream>
#include<fstream>

#define intrare "flip.in"
#define iesire "flip.out"

using namespace std;

int main() {
	ifstream f(intrare);
	ofstream g(iesire);

	int n, m, sum;
	f >> n >> m;
	int A[2000][16];
	sum = 0;
	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			f >> A[i][j];

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

	g << sum;
	
	return 0;
}