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: [14.587, 49.21, -21.274, -54.714, 243.935, 218.436]
Example Output: 75.03

Example Input: [224.567, -42.213, 232.017]
Example Output: 138.124

Example Input: [212.195, 152.682, 81.687, 54.129, 77.845, 220.624, 156.819, 188.596, 63.238]
Example Output:
134.202