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: [140.332, 92.06]
Example Output: 116.196

Example Input: [74.601, 131.018, -45.91]
Example Output: 53.236

Example Input: [166.521, -48.271, 123.84, 217.273, -37.637]
Example Output:
84.345

