// flip.cpp : Defines the entry point for the console application.
//


#include<iostream>
#include<fstream>
using namespace std;


int main()
{
	int m,n,k; long long s1=0,s2=0;
	ifstream input_file("flip.in");
	ofstream book_file("flip.out");
	input_file>>n>>m;
	long long **a=new long long *[n];
	for(int i=0;i<n;i++){a[i]=new long long[m];for(int j=0;j<m;j++)    input_file>>a[i][j];}
q1: k=0;
	for(int i=0;i<n;i++){for(int j=0;j<m;j++) {if(a[i][j]>0) s1+=a[i][j]; else s2+=a[i][j];};
	if((s2*s2)>(s1*s1)) {for(int j=0;j<m;j++) {a[i][j] *= (-1);};};s1=0;s2=0;}
	for(int j=0;j<m;j++){for(int i=0;i<n;i++) {if(a[i][j]>0) s1+=a[i][j]; else s2+=a[i][j];};
	if((s2*s2)>=(s1*s1)) {for(int i=0;i<n;i++) {a[i][j] *= (-1);}k++;};s1=0;s2=0;}	
	if (k) goto q1;
	for(int i=0;i<n;i++) for(int j=0;j<m;j++) s1+=a[i][j];
	book_file<<s1;
	return 0;
}