#include <iostream>
#include <fstream>
using namespace std;
const

int main() {
	int N, M;
	int a[20][20], s, smax = 0;
	ifstream f("flip.in");
	ofstream g("flip.out");
	f >> N>>M;
	
	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++)
		{
			s = 0;
			for (int j = 0;j < M;j++)
			{
				s += a[i][j];
			}
			if (s < 0) {
				for (int j = 0;j < M;j++)
				{
					a[i][j] = -a[i][j];
				}
			}
			
		}
	
	cout << endl;
	for (int i = 0;i < M;i++)
		{
			s = 0;
			for (int j = 0;j < N;j++)
			{
				s += a[j][i];
			}
			if (s < 0) {
				for (int j = 0; j< N;j++)
				{
					a[j][i] = -a[j][i];
				}
			}
		}
	
	for (int i = 0;i < N;i++)
		for (int j = 0;j < M;j++)
		{
			smax += a[i][j];
		}
	g << smax;
	
}