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.

Example Input: [-17.604, 15.108, 34.328, -94.608]
Example Output: -15.694

Example Input: [-9.301, -10.629, 88.777, 68.965]
Example Output: 34.453

Example Input: [213.816, 178.027, 65.849, -91.646, 174.169, -12.033, 48.904, 148.142, 220.714, 218.252]
Example Output:
116.419