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: [153.482, 150.917]
Example Output: 152.2

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

Example Input: [-35.54, 67.735, 184.858, 9.062, 120.196, 39.639, -52.051]
Example Output:
47.7