Qhov xwm ntawm cov hlau nplaum
Cov hlau nplaum muaj ob sab ncov qaum, hlau nplaum sab qaum teb N thiab hlau nplaum sab qab teb S. Tom qab txiav tawm, nws tseem yog ob-ncej N-theem thiab S ncej. Tsis muaj ib tug ncej yuav muaj nyob. Nyob rau tib lub sijhawm, cov hlau nplaum yog qhia. Yog tias koj dai cov hlau nplaum, koj yuav pom tias nws cov ncej sab qab teb taw rau sab laug thiab sab xis ntawm tus ncej sab qab teb, thiab tus ncej qaum teb taw rau sab laug thiab sab qaum teb.