#include<fstream>
using namespace std;
unsigned int n,m;
int a[18][18];
void citire(unsigned int &n, unsigned int &m, int a[18][18]) 
{ifstream f ("flip.in");
 f>>n>>m;
 for(unsigned int i=1;i<=n;i++) 
	 for(unsigned int j=1;j<=m;j++)
		 f>>a[i][j];
 f.close();}
int main()
{citire(n,m,a);
 if(n>m)
	 for(unsigned int i=1;i<=m;i++) {
		 for(unsigned int j=1;j<=n;j++)
			 if(a[j][i]>0) a[0][i]+=a[j][i];
		     else a[n+1][i]+=a[j][i];
	     if(a[n+1][i]>a[0][i]) for(unsigned int j=1;j<=n;j++)
			 a[j][i]*=-1;}
 else
	 for(unsigned int i=1;i<=n;i++) {
		 for(unsigned int j=1;j<=m;j++)
			 if(a[i][j]>0) a[i][0]+=a[i][j];
		     else a[i][n+1]+=a[i][j];
	     if(a[i][n+1]>a[i][0]) for(unsigned int j=1;j<=n;j++)
			 a[i][j]*=-1;}
 unsigned int s=0;
 for(unsigned int i=1;i<=n;i++)
	 for(unsigned int j=1;j<=m;j++)
		 s=s+a[i][j];
 ofstream g ("flip.out");
 g<<s;
 g.close();
 return 0;}