#include <fstream>
using namespace std;

int n, m, a[20][20], s;
ifstream fin("flip.in");
ofstream fout("flip.out");

int main(){
	fin >> n >> m;
	for(int i=1; i<=n; ++i)
		for(int j=1; j<=m; ++j)
			fin >> a[i][j];

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

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

	s = 0;
	for(int i=1; i<=n; ++i)
		for(int j=1; j<=m; ++j)
			s += a[i][j];
	fout << s;
	return 0;
}