#include<iostream.h>
#include<fstream.h>
int main()
{
	ifstream f("flip.in");
	ofstream g("flip.out");
	int i,j,m,n,k; f>>n>>m; long x[n][m],y=0,z=0,s=0;
	for (i=1;i<=n;i++)
	{
		for (j=1;j<=m;j++) 
		{
			f>>x[i][j];
			if (x[i][j]<0) z=z-x[i][j]; 
			else y=y+x[i][j];
		}
		if (y<z)
		for (k=1;k<=m;k++) x[i][k]*=-1;
		z=0; y=0;
	}
	for (i=1;i<=m;i++)
	{
		for (j=1;j<=n;j++) 
		{
			if (x[j][i]<0) z=z-x[j][i]; 
			else y=y+x[j][i];
		}
		if (y<z) 
		for (k=1;k<=n;k++) {x[k][i]*=-1; s+=x[k][i];}
		else for (k=1;k<=n;k++) s+=x[k][i];
		z=0; y=0;
	}
	g<<s;
}