#include <stdio.h>
FILE *f=fopen("flip.in","r"), *g=fopen("flip.out","w");
int q,w,n,m,lin[20],x[20][20],y[20][20],z;
long s,max=0;
void init(int k)
	{
	lin[k]=-1;
	}

int succesor(int k)
	{
	if (lin[k]<1)
		{
		lin[k]++;
		return 1;
		}
	else return 0;
	}

int solutie(int k)
	{
	return k==n+1;
	}

void use()
	{
	s=0;
	for (q=1;q<=n;q++)
		if (lin[q])
			for (w=1;w<=m;w++)
				y[q][w]*=-1;
	for (w=1;w<=m;w++)
		for (q=1;q<=n;q++)
			{
			s+=x[q][w];
			if (q==n)
				{
				if (s<0)
					{
					for (z=1;z<=n;z++)
						x[z][w]*=-1;
					}
				s=0;
				}
			}
	s=0;
	for (q=1;q<=n;q++)
		for (w=1;w<=m;w++)
			{
			s+=y[q][w];
			y[q][w]=x[q][w];
			}
	if (s>max) max=s;
	}

void back(int k)
	{
	if (solutie(k)) use();
		else
			{
			init(k);
			while (succesor(k))
				back(k+1);
			}
	}

int main()
{
int i,j,k,p,s,min;
fscanf(f,"%d %d",&n,&m);
for (i=1;i<=n;i++)
	for (j=1;j<=m;j++)
		{
		fscanf(f,"%d",&x[i][j]);
		y[i][j]=x[i][j];
                }
back(1);
fprintf(g,"%ld\n",max);
fclose(g);
return 0;
}