#include<stdio.h>
FILE *f=fopen("flip.in","r"),*g=fopen("flip.out","w");
int n,m,i,j,s1,s2,a[17][17],k,x[3][17];

int main()
{
	fscanf(f,"%d%d",&n,&m);
	for(i=1;i<=n;i++)
		{
			s1=0;s2=0;
			for(j=1;j<=m;j++)
				{
					fscanf(f,"%d",&a[i][j]);
					if(a[i][j]<0)
						s1+=a[i][j];
							else
								s2+=a[i][j];
				}
			for(k=1;k<=m;k++)
				{
					if(-s1>s2)
						a[i][k]=-a[i][k];
					if(a[i][k]<0)
						x[1][k]+=a[i][k];
					else
						x[2][k]+=a[i][k];
				}
		}
	s1=0;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			if(-x[1][j]>x[2][j])
				s1+=-a[i][j];
			else
				s1+=a[i][j];
	fprintf(g,"%d",s1);		
	return 0;
}