#include<iostream>
#include<fstream>
using namespace std;
ifstream in("flip.in");
ofstream out("flip.out");
int s1=0,s2=0,n,i,j,a[50][50],p,k,suma=0;
void citire()
{
	in>>n;in>>p;
	for(i=1;i<=n;i++)
		for(j=1;j<=p;j++)
			in>>a[i][j];
	in.close();
}
int main()
{
	citire();
	/*for(i=1;i<=n;i++)
		for(j=1;j<=p;j++)
			out<<a[i][j];*/
	for(i=1;i<=n;i++)
		{
		for(j=1;j<=p;j++)
		{
			s1=s1+a[i][j];
			s2=s2+(-1*a[i][j]);
		}
		if(s1<s2)
			for(k=1;k<=p;k++)
					a[i][k]=-1*a[i][k];
		}
	s1=0;s2=0;
	for(j=1;j<=p;j++)
		{
		for(i=1;i<=n;i++)
		{
			s1=s1+a[j][i];
			s2=s2+(-1*a[j][i]);
		}
		if(s1<s2)
			for(k=1;k<=n;k++)
				a[j][k]=-1*a[j][k];
		}
	for(i=1;i<=n;i++)
		for(j=1;j<=p;j++)
			suma=suma+a[i][j];
	out<<suma;
	out.close();
	return 0;
}