#include <stdlib.h>
#include <stdint.h>
#include <string>
#include <vector>
#include <iostream>
#include <unordered_map>
#include <memory>
#include <algorithm>
#include <deque>
#include <iterator>
#include <numeric>
#include <assert.h>
#include <cstdlib>
#include <sstream>
#include <fstream>

#define INPUT_PATH ""
#define OUTPUT_PATH ""

void algorithm();

int main()
{
  algorithm();
  return 0;
}
using namespace std;

namespace
{
  void flipCol(vector<int>& matrix, int col, int nrRows, int nrCols) 
  {
    for (int row = 0; row < nrRows; ++row)
    {
      matrix[row*nrCols + col] = -matrix[row*nrCols + col];
    }
  }
  void tryFlippingRows(int& maxSum, int sum, int row, bool sign, int nrCols, int nrRows, vector<int>& matrix)
  {
    for (int col = 0; col < nrCols; ++col)
    {
      sum += sign ? matrix[row*nrCols + col] : -matrix[row*nrCols + col];
    }
    maxSum = max(maxSum, sum);
    if (row + 1 < nrRows)
    {
      tryFlippingRows(maxSum, sum, row + 1, true, nrCols, nrRows, matrix);
      tryFlippingRows(maxSum, sum, row + 1, false, nrCols, nrRows, matrix);
    }
  }

  int tryFlippingRows(int nrCols, int nrRows, vector<int>& matrix)
  {
    int sum = 0;
    int maxSum = 0;
    tryFlippingRows(maxSum, sum, 0, true, nrCols, nrRows, matrix);
    tryFlippingRows(maxSum, sum, 0, false, nrCols, nrRows, matrix);
    return maxSum;
  }

  void tryFlippingCols(int& maxSum, int col, bool sign, int nrCols, int nrRows, vector<int>& matrix)
  {
    int sum = tryFlippingRows(nrCols, nrRows, matrix);
    maxSum = max(sum, maxSum);
    if (col + 1 < nrCols)
    {
      tryFlippingCols(maxSum, col + 1, true, nrCols, nrRows, matrix);
      flipCol(matrix, col + 1, nrRows, nrCols);
      tryFlippingCols(maxSum, col + 1, false, nrCols, nrRows, matrix);
    }
  }

  int startFlipping(int nrCols, int nrRows, vector<int>& matrix)
  {
    int maxSum = 0;
    tryFlippingCols(maxSum, 0, true, nrCols, nrRows, matrix);
    tryFlippingCols(maxSum, 0, false, nrCols, nrRows, matrix);
    return maxSum;
  }
}

////////////////////////////////////////////////////////////////////////////////
void algorithm()
{
  ifstream inputFile(INPUT_PATH "flip.in");
  ofstream outputFile(OUTPUT_PATH "flip.out");

  //read data from file
  int nrRows = 0; inputFile >> nrRows;
  int nrCols = 0; inputFile >> nrCols;

  vector<int> matrix; 
  matrix.reserve(nrRows*nrCols);

  int readVal = 0;
  while (inputFile >> readVal)
  {
    matrix.push_back(readVal);
  }
  //end read data from file

  int maxSum = startFlipping(nrCols, nrRows, matrix );

  outputFile << maxSum;

  inputFile.close();
  outputFile.close();
}