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

double start,stop;

int main()
{	
	start=clock();
	int N,M,a[17][17],i,j;
	int sum,sumcont,S;
	ifstream f("flip.in");
	ofstream g("flip.out");
	f>>N>>M;
	for(i=1;i<=N;i++)
		for(j=1;j<=M;j++)
			f>>a[i][j];
	int sem;
	do{
	sem=1;
	for(i=1;i<=N;i++)
		{	
			sum=0;
			sumcont=0;
			for(j=1;j<=M;j++)
				{sum =sum + a[i][j];
				sumcont =sumcont + a[i][j]*(-1);}
			if (sum<sumcont)
				for(j=1;j<=M;j++)
					{a[i][j] =a[i][j]* (-1);sem=0;}
		}
	for(j=1;j<=M;j++)
	{	
		sum=0;
		sumcont=0;
		for(i=1;i<=N;i++)
			{sum = sum + a[i][j];
				sumcont =sumcont + a[i][j]*(-1);}
		if (sum<sumcont)
				for(i=1;i<=N;i++)
					{a[i][j] =a[i][j] * (-1);sem=0;}
	}
	}
	while(sem==0);
	S=0;
	for(i=1;i<=N;i++)
		for(j=1;j<=M;j++)
			S =S + a[i][j];
	g<<S;
	f.close();
	g.close();
	stop=clock();
	cout<<(stop-start)/CLOCKS_PER_SEC;
	return 0;
}