#include <stdio.h>
int m,n,i,k,matrix[17][17];
long long sum,summax = 16000001;

FILE * in = fopen("flip.in","rt");
FILE * out = fopen("flip.out","wt");

int main()
{
	fscanf(in,"%d",&m);
	fscanf(in,"%d",&n);
	
	for(i=1;i<=m;i++)
		for(k=1;k<=n;k++)
			fscanf(in,"%d",&matrix[i][k]);
		
	for(i=1;i<=m;i++)
	{
		for(k=1;k<=n;k++)
			sum = sum + matrix[i][k];
		
		if(sum < 0)
			for(k=1;k<=n;k++)
				matrix[i][k] = -matrix[i][k];
		
		sum = 0;
	}
	
	/*for(i=1;i<=m;i++)
	{
		for(k=1;k<=n;k++)
			printf("%d ",matrix[i][k]);
		printf("\n");
	}*/
	
	for(i=1;i<=n;i++)
	{
		for(k=1;k<=m;k++)
			sum = sum + matrix[k][i];
		//printf("%I64d\n",sum);
		
		if(sum < 0)
			for(k=1;k<=m;k++)
				matrix[k][i] = -matrix[k][i];
		
		sum = 0;
	}
	
	/*for(i=1;i<=m;i++)
	{
		for(k=1;k<=n;k++)
			printf("%d ",matrix[i][k]);
		printf("\n");
	}*/
	
	sum = 0;
	
	for(i=1;i<=m;i++)
		for(k=1;k<=n;k++)
			sum = sum + matrix[i][k];
	
		
	fprintf(out,"%I64d\n",sum);
	
	return (0);
}