You are given a math word problem and you are supposed to only use subtraction on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
One example is below.
Q: Context: Sam is 6 feet tall and Alex is 5 feet tall 

 Question: By how many feet is Sam taller than Alex? 
A: 1
Rationale:  Sam's height - Alex's height = 6-5 = 1
Q: Context: Bobby ate 17 pieces of candy. Then he ate 15 more. If he initially had 36 pieces of candy 

 Question: How many pieces of candy does he still have left?
A:
4