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

int n, m;
int a[17][17];
bool 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];
    }
  }

  // Find the most negative row or column and invert it,
  // until no more negative rows or columns exist.
  int min_sum = -1;
  while (min_sum < 0) {
    min_sum = 0;
    int min_index;
    int is_row;
    for (int i = 0; i < n; i++) {
      int sum = 0; 
      for (int j = 0; j < m; j++) {
        sum += a[i][j];
      }
      if (sum < min_sum) {
        min_sum = sum;
        min_index = i;
        is_row = true;
      }
    }
    for (int j = 0; j < m; j++) {
      int sum = 0; 
      for (int i = 0; i < n; i++) {
        sum += a[i][j];
      }
      if (sum < min_sum) {
        min_sum = sum;
        min_index = j;
        is_row = false;
      }
    } 
    if (min_sum < 0) {
      if (is_row) {
        for (int j = 0; j < m; j++) {
          a[min_index][j] = -a[min_index][j];
        }
      } else {
        for (int i = 0; i < n; i++) {
          a[i][min_index] = -a[i][min_index];
        }
      }
    }
  }
  // Calculate the matrix sum
  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;
}