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: [-66.271, 56.586, -21.072, 136.915, 54.951, 112.054]
Example Output: 45.527

Example Input: [211.292, 92.275, 128.423, 242.327, -54.053, 89.501, 64.784]
Example Output: 110.65

Example Input: [-17.106, 23.8, -54.195, 233.82, -99.732, -68.488, 215.616]
Example Output:
33.388