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: [176.017, -45.57]
Example Output: 65.224

Example Input: [220.903, 155.959]
Example Output: 188.431

Example Input: [120.163, 21.332, 13.22]
Example Output:
51.572