You are given a math word problem and you are supposed to apply a single mathematical operator like addition, subtraction, multiplication, or division on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

Example Input: there are 12 birds on the fence . 8 more birds land on the fence . how many birds are on the fence ?
Example Output: 20

Example Input: a chef used 39 cherries to make a pie . now he has 58 cherries left . how many cherries did he have before he made the pie ?
Example Output: 97

Example Input: a clown had 16 balloons . he gave 4 away at a party . what 's the difference between the number of balloons the clown had in the beginning and he gave away at a party ?
Example Output:
12