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: [-63.278, 115.92, 179.699, 73.157]
Example Output: 76.374

Example Input: [159.291, 160.61, -50.992, 34.053, 78.883, 222.627, 105.95]
Example Output: 101.489

Example Input: [159.4, 171.158, 208.441, 137.746, 78.097, 223.679, 142.855, 50.38, 165.77, 228.185]
Example Output:
156.571