#include <fstream>
#include <string>
using namespace std;
long int g_lnMatrix[16][16];
int g_nVerticalSize = 1, g_nHorizontalSize = 1, g_nLargestSum = 0;
string Line = "Line", Column = "Column";

void Flip (const int &rnIndex, string strWhat)
{
    for (int iii = 0; iii < ((strWhat == "Line") ? g_nVerticalSize : g_nHorizontalSize); iii++)
        ((strWhat == "Line") ? g_lnMatrix[iii][rnIndex] : g_lnMatrix[rnIndex][iii]) *= -1;
}

long int CalculateSum ()
{
    long int lnSum = 0;
    for (int iii = 0; iii < g_nVerticalSize; iii++)
        for (int jjj = 0; jjj < g_nHorizontalSize; jjj++)
            lnSum += g_lnMatrix[iii][jjj];
    return lnSum;
}

void Permutations (int nVertIndex, int nHorizIndex)
{
    if (nHorizIndex == g_nHorizontalSize)
    {
        long int lnSum = CalculateSum ();
		if (lnSum > g_nLargestSum)
			g_nLargestSum = lnSum;
    }
    else if (nVertIndex == g_nVerticalSize)
    {
		Permutations (nVertIndex, nHorizIndex + 1);
        Flip (nHorizIndex, Line);
		if (CalculateSum () < 0)
			return;
		Permutations (nVertIndex, nHorizIndex + 1);
    }
    else
    {
		Permutations (nVertIndex + 1, nHorizIndex);
		Flip (nVertIndex, Column);
		Permutations (nVertIndex + 1, nHorizIndex);
    }
}

int main ()
{
    ifstream in ("flip.in");
    in >> g_nVerticalSize >> g_nHorizontalSize;
    for (int iii = 0; iii < g_nVerticalSize; iii++)
        for (int jjj = 0; jjj < g_nHorizontalSize; jjj++)
            in >> g_lnMatrix[iii][jjj];
    in.close();
	
    Permutations (0, 0);
	
	ofstream out ("flip.out");
	out << g_nLargestSum;
	out.close();

    return 0;
}