#include <fstream>
using namespace std;
#define maxim 16
ifstream fin ("flip.in");
ofstream fout ("flip.out");
int n,m,x[maxim][maxim];
long s;
bool verif=0;
int main(){
    fin>>n>>m;
    for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)fin>>x[i][j];
    while(!verif){
        verif=1;
        //linii
        for(int i=1;i<=n;i++)
        {
            s=0;
            for(int j=1;j<=m;j++)s+=x[i][j];
            if(s<0){for(int j=1;j<=m;j++)x[i][j]*=-1; verif=0;}
        }
        //coloane
        for(int j=1;j<=m;j++)
        {
            s=0;
            for(int i=1;i<=n;i++)s+=x[i][j];
            if(s<0){for(int i=1;i<=n;i++)x[i][j]*=-1; verif=0;}
        }
    }
    s=0;
    for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)s+=x[i][j];
    fout<<s;
    return 0;
}