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

Example Input: [182.852, 102.398, 200.428, -71.943, 50.578, -59.389, 0.465]
Example Output: 57.913

Example Input: [217.301, 19.358, -21.02, -51.249]
Example Output:
41.098