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: [237.501, 67.08, 13.857]
Example Output: 106.146

Example Input: [128.472, 149.361, 71.023, -96.651]
Example Output: 63.051

Example Input: [178.096, 125.072, -59.462, 70.309]
Example Output:
78.504