#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int main () {
	long long n,m,i,j,t[16][16],s=0,k,sum=0,suma=0;
	fin>>n>>m;
	for (i=1; i<=n; ++i) {
		for (j=1; j<=m; ++j) {
			fin>>t[i][j];
			s=s+t[i][j];}
		if (s<0) { for (k=1;k<=m;++k) t[i][k]=t[i][k]*-1; }
		s=0;
			}
		for (i=1; i<=m; ++i) {
		for (j=1; j<=n; ++j)
		sum=sum+t[j][i];
		if (sum<0) { for (k=1;k<=n;++k) t[k][i]=t[k][i]*-1; }
		sum=0; }
	for (i=1; i<=n; ++i) {
		for (j=1; j<=m; ++j)
		suma+=t[i][j]; }
		fout<<suma;
		return 0;
	}