#include<fstream.h>

int main()
{	int n,m;
	long sir[17][17],i,j,k,s=1;
	double suma;
	ifstream in("flip.in");
	in>>n>>m;
	while(s<=n)
	{for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			in>>sir[i][j];
	in.close();
	for(i=1;i<=n;i++)
	{       suma=0;
		for(j=1;j<=m;j++)
			suma=suma+sir[i][j];

		if(suma<0)
			for(k=1;k<=m;k++)
				sir[i][k]=sir[i][k]*-1;
	}
	for(i=1;i<=m;i++)
	{	suma=0;
		for(j=1;j<=n;j++)
			suma=suma+sir[j][i];
		if(suma<0)
			for(k=1;k<=n;k++)
				sir[k][i]=sir[k][i]*-1;

	}s++;
	}
	suma=0;
	ofstream out("flip.out");
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			suma=suma+sir[i][j];

	out<<suma;
	out.close();
	return 0;
}