#include<stdio.h>
FILE *fin=fopen("flip.in", "r");
FILE *fout=fopen("flip.out", "w");
int n,m,i,j;
float suma,suma_aux1,suma_aux2;
float a[16][16];
int main(){
	fscanf(fin, "%d", &n);
	fscanf(fin, "%d", &m);
	
	for (i=1; i<=n; i++)
		for (j=1; j<=m; j++)
			fscanf(fin, "%f", &a[i][j]);
	
	for (i=1; i<=n; i++)
	{
		suma_aux1=0;
		suma_aux2=0;
		for (j=1; j<=m; j++)
		{
			suma_aux1+=a[i][j];
			suma_aux2+=(-a[i][j]);
		}
		if(suma_aux2>=suma_aux1)
			for (j=1; j<=m; j++)
				a[i][j]=-a[i][j];
	}
	for (j=1; j<=m; j++)
	{
		suma_aux1=0;
		suma_aux2=0;
		for (i=1; i<=n; i++)
		{
			suma_aux1+=a[i][j];
			suma_aux2+=(-a[i][j]);
		}
		if(suma_aux2>=suma_aux1)
			for (i=1; i<=n; i++)
				a[i][j]=-a[i][j];
	}
	suma=0;
	for (i=1; i<=n; i++)
		for (j=1; j<=m; j++)
			suma+=a[i][j];
	fprintf(fout, "%.0f", suma);
	
	fclose(fin);
	fclose(fout);
	return 0;
	
}