#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;
	for(int i =1;i<=N;i++){
		long long suma = 0;
		for(int j =1;j<=M;j++){
			in >> v[i][j];
			sumaH[j] += v[i][j];
			suma += v[i][j];
			if(j==M)
				if(suma*-1 > suma)
					for(int x =1;x<=M;x++)
						v[i][x]*=-1;

		}
		if(i==N)
			for(int j = 1;j<=M;j++){
                if(sumaH[j]*-1 > sumaH[j])
					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];
			}
	}
	out << sum_f;
}