# include <cstdio>
using namespace std;
int sp,sn,n,m,x,S,actionat,dif,a[20][20];
int main ()
{
    freopen ("flip.in", "r", stdin);
    freopen ("flip.out", "w", stdout);
    int i,j;
    dif=1000000;
    scanf ("%d%d", &n,&m);
    for (i=1; i<=n; ++i)
         for (j=1; j<=m; ++j)
              {
                  scanf ("%d", &x);
                  a[i][j]=x;
              }

    for (i=1; i<=n; ++i)
        {
            sp=0;
            sn=0;
            for (j=1; j<=m; ++j)
                {
                    if (a[i][j]>0) sp+=a[i][j];
                       else sn=sn-a[i][j];
                }
            if (sp>sn) {
                         S+=sp;
                         x=sp-sn;
                         if (x<dif && x>=1) dif=x;
                       }
               else {
                        S+=sn;
                        actionat=1;
                        for (j=1; j<=m; ++j)
                            a[i][j]=a[i][j]*-1;
                    }
        }
    printf ("%d\n", S);

    return 0;
}