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: [224.567, -42.213, 232.017]
Example Output: 138.124

Example Input: [32.131, 116.887, 66.741, 218.719, 106.049, -93.999]
Example Output: 74.421

Example Input: [173.164, -92.215, 230.455]
Example Output:
103.801