#include <iostream>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
long long int n, m, suma=0;
long long int v[1000][1000];
int main()
{
	fin>>n>>m;
	for(int i=1;i<=n;++i)
	{
		for(int j=1;j<=m;++j)
		{
			fin>>v[i][j];
		}
	}
	for(int i=1;i<=n;++i)
	{
		int suma_mic=0, suma_mare=0;
		for(int j=1;j<=m;++j)
		{
			if(v[i][j]<0)
			{
				suma_mic+=v[i][j];
			}
			else
			{
				suma_mare+=v[i][j];
			}
		}
		if(suma_mic*(-1)>suma_mare)
		{
			for(int j=1;j<=m;++j)
			{
				v[i][j]*=(-1);
			}
		}
	}
	for(int j=1;j<=m;++j)
	{
		int suma_mic=0, suma_mare=0;
		for(int i=1;i<=n;++i)
		{
			if(v[i][j]<0)
			{
				suma_mic+=v[i][j];
			}
			else
			{
				suma_mare+=v[i][j];
			}
		}
		if(suma_mic*(-1)>suma_mare)
		{
			for(int i=1;i<=n;++i)
			{
				v[i][j]*=(-1);
			}
		}
	}	
	for(int i=1;i<=n;++i)
	{
		for(int j=1;j<=m;++j)
			suma+=v[i][j];
	}
	fout<<suma;
}