#include<iostream>
#include<string>
#include<stdlib.h>
#include<fstream>
#include <time.h> 
#include <algorithm>

using namespace std;

int main()
{
    ifstream in("flip.in");
    ofstream of("flip.out");
	int a,b,i,j;
	float c[100][100],suma=0,total=0;
	in>>a>>b;
	for(i=1;i<=a;i++)
		for(j=1;j<=b;j++)
			in>>c[i][j];
		
		
			for(i=1;i<=a;i++)
		{for(j=1;j<=b;j++)
			suma=suma+c[i][j];
		if(suma<0)
			{for(j=1;j<=b;j++)
				c[i][j]=c[i][j]*(-1);}
		suma=0;}	
			
		for(j=1;j<=b;j++)
		{for(i=1;i<=a;i++)
			suma=suma+c[i][j];
		if(suma<0)
			{for(i=1;i<=a;i++)
				c[i][j]=c[i][j]*(-1);}
		suma=0;}		
				
			
		for(i=1;i<=a;i++)
			for(j=1;j<=b;j++)
				{
				total=total+c[i][j];
				}

			
			
		
		
		
	of<<total;
	cout<<total;
	
	in.close();
	of.close();
}