#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>



int main()
{
	int n, m,a[100][100],s1,s2;
	scanf("%d%d", &n, &m);
	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			scanf("%d", &a[i][j]);

	for (int i = 0; i < m; i++)
	{
		s1 = 0;
		s2 = 0;
		for (int j = 0; j < n; j++)
			{
			s1 = s1 + a[j][i];
			s2 = s2 + (-a[j][i]);
			}
		if (s1 < s2)
		{
			for (int w = 0; w < n; w++)
				a[w][i] = a[w][i] * -1;
		}
	}

	for (int i = 0; i < n; i++)
	{
		s1 = 0;
		s2 = 0;
		for (int j = 0; j < m; j++)
		{
			s1 = s1 + a[i][j];
			s2 = s2 + (-a[i][j]);
		}
		if (s1 < s2)
			for (int w = 0; w < m; w++)
				a[i][w] = -a[i][w];
	}
	int s=0;
	
	for (int i = 0; i < n; i++)
		for (int j = 0; j < m; j++)
			s = s + a[i][j];

	printf("%d", s);


}