#include <stdio.h>
#include <fstream>
using namespace std;

#define N 16

ifstream fin("flip.in");
ofstream fout("flip.out");

int matrix[N][N], line[N], col[N];

int main()
{
	int n, m, i, j;
	int sum = 0;

	fin >> n >> m;

	for (i = 0; i < n; i++) 
	{
		line[i] = 0;
		for (j = 0; j < m; j++)
		{
			fin >> matrix[i][j];
			line[i] += matrix[i][j];
			col[j] += matrix[i][j];
		}

	}



	for (i = 0; i < n; i++)
	{
		if (line[i] < 0)
		{
			for (j = 0; j < m; j++)
			{
				matrix[i][j] *= -1;
			}
		}
	}

	for (i = 0; i < m; i++)
	{
		if (col[i] < 0) 
		{
			for (j = 0; j < n; j++)
			{
				matrix[j][i] *= -1;
			}
		}
	}

	for (i = 0; i < n; i++)
	{
		for (j = 0; j < m; j++)
		{
			sum += matrix[i][j];
		}
	}

	fout << sum << '\n';

	fin.close();
	fout.close();
	return 0;
}