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: [159.965, 172.082]
Example Output: 166.024

Example Input: [216.883, -37.346, 67.498, 41.686, 140.857, 195.57]
Example Output: 104.191

Example Input: [238.567, 35.755]
Example Output:
137.161