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: [22.971, 146.947, 84.327, 123.65, -30.682, -43.973, 211.836, 146.398, -65.992]
Example Output: 66.165

Example Input: [-81.432, -63.059, 150.144, 55.203, 215.405, -89.797, 72.946]
Example Output: 37.059

Example Input: [205.744, -5.99, 197.154, 8.13, 191.973]
Example Output:
119.402