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: [73.603, -84.154, 222.739, 205.594, 215.842]
Example Output: 126.725

Example Input: [-87.239, 176.019, -5.769, -11.992, 180.644, -27.711, -85.106, 140.235, 100.673]
Example Output:
42.195