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: [70.553, 193.054, 166.173, 115.812]
Example Output: 136.398

Example Input: [194.983, -22.961, 95.798, -2.34, 178.547, -90.942, 122.52, 109.389]
Example Output: 73.124

Example Input: [103.118, 90.25, 4.835]
Example Output:
66.068