#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream in("flip.in");
    ofstream out("flip.out");

	short N,M;
	in >> N >> M;
	long long v[N][M];
	long long sumaH[M];
	long long sum_f = 0;
	if(M==1 && N==1)
    {
        in >> v[1][1];
        if(v[1][1]<0)
            out << v[1][1]*-1;
        else
            out << v[1][1];
        return 0;
    }
	for(int i =1;i<=M;i++)
        sumaH[i]=0;
	for(int i =1;i<=N;i++){
		long long suma = 0;
		for(int j =1;j<=M;j++){
			in >> v[i][j];
			suma += v[i][j];
			//sumaH[j] += v[i][j];
			if(j==M){
				if(suma*-1 > suma)
					for(int x =1;x<=M;x++){
						v[i][x]*=-1;
						//sumaH[j] += v[i][x];
					}
			}
		}
		if(i==N){
                for(int j = 1;j<=M;j++){
                    int suma = 0;
                    for(int f = 1;f<=N;f++)
						suma += v[f][j];

                    if(suma*-1 > suma)
                        for(int x =1;x<=N;x++){
                            v[x][j]*=-1;
                            sum_f+=v[x][j];
                        }
                    else
                        for(int x =1;x<=N;x++)
                            sum_f+=v[x][j];
                }
			}
		}
		/*
    for(int i =1;i<=N;i++){
        for(int f=1;f<=M;f++)
        out << v[i][f] << " ";
    out << endl;
    }
    */
    out << sum_f;
    return 0;
}