#include<cstdio>
int s1,s2,s,a[30][30],i,j,n,m;
int main()
{
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            scanf("%d",&a[i][j]);
    for(i=1;i<=n;i++)
    {
        s1=0;
        s2=0;
        for(j=1;j<=m;j++)
        {
            s1+=a[i][j];
            s2+=-a[i][j];
        }
        if(s2>s1)
        {
            for(j=1;j<=m;j++)
                a[i][j]=-a[i][j];
        }
    }
    for(j=1;j<=m;j++)
    {
        s1=0;
        s2=0;
        for(i=1;i<=n;i++)
        {
            s1+=a[i][j];
            s2+=-a[i][j];
        }
        if(s2>s1)
        {
            for(i=1;i<=n;i++)
                a[i][j]=-a[i][j];
        }
    }
    s=0;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            s+=a[i][j];
    printf("%d",s);
    return 0;
}