Given a math word problem, answer the following question. You might need to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the question and then only report the final numerical answer.

Ex Input:
randy has 78 blocks . he uses 19 blocks to build a tower . how many blocks are left ?

Ex Output:
59

Ex Input:
isha 's pencil is 31 inches long . if she sharpens it now her pencil is 14 inches long . how much did she sharpen off of her pencil ?

Ex Output:
17

Ex Input:
tripp and charlotte are going on a 36 mile hike . tripp 's backpack weighs 25 pounds . charlotte 's back pack weighs 7 pounds less . they hiked 9 miles the first day . how many miles do they have left ?

Ex Output:
27