#include <fstream>
using namespace std;

int main ()
{
  ifstream cin ("flip.in");
  ofstream cout("flip.out");

  int m, n;
  cin >> m >> n;

  int ma[17][17];

  for (int i = 1; i <= m; ++i)
    for (int j = 1; j <= n; ++j)
      cin >> ma[i][j];

  // suma pe linii
  for (int i = 1; i <= m; ++i)
    {
      int suma = 0;
      for (int j = 1; j <= m; ++j)
	suma += ma[i][j];

      if (suma < suma * (-1))
	for (int j = 1; j <= m; ++j)
	  ma[i][j] *= -1;
    }

  // suma pe coloane
  for (int i = 1; i <= m; ++i)
    {
      int suma = 0;
      for (int j = 1; j <= m; ++j)
	suma += ma[j][i];

      if (suma < suma * (-1))
	for (int j = 1; j <= m; ++j)
	  ma[j][i] *= -1;
    }  

  int suma = 0;
  for (int i = 1; i <= m; ++i)
    for (int j = 1; j <= n; ++j)
      suma += ma[i][j];

  cout << suma;
}