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

int n, m;
int a[17][17];
bool invertion = true;

void invert_rows() 
{
  // Invert negative rows
  for (int i = 0; i < n; i++) {
    long int 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] = -a[i][j];
        invertion = true;
      }
    }
  }
}

void invert_cols() 
{  
  // Invert negative columns 
  for (int j = 0; j < m; j++) {
    long int 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] = -a[i][j];
        invertion = true;
      }
    }
  }
}


int main()
{
  ifstream input("flip.in");
  input >> n >> m;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      input >> a[i][j];
    }
  }

  while (invertion) {
    invertion = false;
    invert_rows();
    invert_cols();
  }

  // Calculate the matrix sum
  long int sum = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      sum += a[i][j];
    }
  }

  ofstream output("flip.out");
  output << sum;
}