#include<fstream>
#include<iostream>
using namespace std;
fstream f("flip.in",ios::in);
fstream g("flip.out",ios::out);

long v[1000][1000];
	int n,m;
	long sum1=0,sum2=0,i,j;
	
void citire()
{
	f>>n>>m;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
		f>>v[i][j];
}


int main(void)
{
	
	citire();
	for(i=1;i<=n;i++)
	{
		sum1=0;
		for(j=1;j<=m;j++)
		{
			sum1+=v[i][j];
			if(sum1<0)
				for(j=1;j<=m;j++)
					v[i][j]*=-1;
		}
	}
	for(j=1;j<=m;j++)
	{
		sum1=0;
		for(i=1;i<=n;i++)
		{
			sum1+=v[i][j];
			if(sum1<0)
				for(i=1;i<=n;i++)
					v[i][j]*=-1;
		}
	}
	sum1=0;
	for(i=1;i<=n;i++)
		for(j=1;j<=m;j++)
			sum1+=v[i][j];
	g<<sum1;
}