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: [-98.163, -66.763, 149.544, -89.893, -10.155]
Example Output: -23.086

Example Input: [-40.246, -7.512, 174.245, -98.6]
Example Output: 6.972

Example Input: [133.784, 42.281, -25.121, 190.377, 179.979, 210.94, 213.849, 145.965]
Example Output:
136.507