A wire of resistance $ R $ is bent into a triangular pyramid as shown in the figure, with each segment having the same length. The resistance between points $ A $ and $ B $ is $ \frac{R}{n} $. The value of $ n $ is:

Rearrange the following parts to form a meaningful and grammatically correct sentence: 
P. a healthy diet and regular exercise 
Q. are important habits 
R. that help maintain good physical and mental health 
S. especially in today's busy world