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.

Example Input: thanksgiving is coming and dr. mary wants to celebrate it by sharing her blessing to different charities . she first went to oldtown where she donated $ 700 in total to 3 different nursing homes . if she gave $ 245 to the first home and $ 225 to the second how much did she give to the third home ?
Example Output: 230

Example Input: john threw a halloween party where 13 people showed up . if only 6 dressed up how many people did n't wear costumes ?
Example Output: 7

Example Input: charlie an aspiring inventor is planning to make some wings to fulfill his dream to fly around the world . he started by collecting feathers . he needs 900 feathers and he already has 387 how many more feathers does he need to collect ?
Example Output:
513