#include <stdio.h>
#include <stdlib.h>

int main()
{
	FILE *in, *out;
	int l, c, i, j, sum;
	int mat[17][17];
	in = fopen("flip.in", "rt");
	if(fscanf(in, "%d %d", &l, &c)==2)
	while(!fscanf(in, "%d", &mat[i][j]))
	{
		i++;
		j++;
	}
	fclose(in);
	for(j = 0; j < c; j++)
	{
		sum = 0;
		for(i = 0; i < l; i++)
			sum += mat[i][j];
		if (sum < 0)
			for(i = 0; i < l; i++)
				mat[i][j] = -mat[i][j];
	}
	for(i = 0; i < l; i++)
	{
		sum = 0;
		for(j = 0; j < c; j++)
			sum += mat[i][j];
		if (sum < 0)
			for(j = 0; j < c; j++)
				mat[i][j] = -mat[i][j];
	}
	
	int totalSum = 0;
	for(i = 0; i < l; i++)
		for(j = 0; j < c ; j++)
			totalSum += mat[i][j];
	out = fopen("flip.out", "wt");
	fprintf(out, "%d", totalSum);
	fclose(out);	
	return 0; 
}