#include<iostream>
#include<fstream>
using namespace std;
int main()
{
	int a[100][100], n, coloane = 0, m, i, j, linii = 0, s = 0, s1 = 0, sum1 = 0, sum = 0, suma = 0;
	ifstream g("flip.in");
	ofstream f("flip.out");
	g >> n >> m;
	for (i = 0; i < n; i++)
		for (j = 0; j < m; j++)
			g >> a[i][j];
		while (coloane <= m)
		{
			for (i = 0; i < n; i++)
			{
				s = s + a[i][coloane];
				s1 = s1 + (a[i][coloane] * (-1));
			}
			if (s < s1)
			{
				for (i = 0; i < n; i++)
					a[i][coloane] = a[i][coloane] * (-1);
			}
			s = 0;
			s1 = 0;
			coloane++;
		}
		while (linii <= n)
		{
			for (j = 0; j < n; j++)
			{
				sum = sum + a[linii][j];
				sum1 = sum1 + (a[linii][j] * (-1));
			}
			if (sum1>sum)
			{
				for (j = 0; j < m; j++)
					a[linii][j] = a[linii][j] * (-1);
			}
				sum1 = 0;
				sum = 0;
				linii++;
		}
		for (i = 0; i < n; i++)
		{
			for (j = 0; j < m; j++)
				suma = suma + a[i][j];
		}
		f << suma;
}