#include<cstdio>
using namespace std;
int n,m;
long a[20][20];
int main()
{
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            scanf("%lld",&a[i][j]);
    for (int i=1;i<=n;i++)
        {
            long s=0;
            for (int j=1;j<=m;j++)
                s+=a[i][j];
            if (s<0)
            for (int j=1;j<=m;j++) a[i][j]=a[i][j]*-1;
        }
    for (int j=1;j<=m;j++)
        {
            long s=0;
            for (int i=1;i<=n;i++)
                s+=a[i][j];
            if (s<0)
            for (int i=1;i<=n;i++) a[i][j]=a[i][j]*-1;
        }
    long long s1=0;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++) s1+=a[i][j];
    printf("%lld",s1);
    return 0;
}