Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [-18.16, 80.684, -5.241, -49.209, -8.776, -87.119, 210.033]

17.459