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: [22.306, 72.768, 218.947, 52.973, 100.121, 157.59, -92.109]
Example Output: 76.085

Example Input: [140.332, 92.06]
Example Output: 116.196

Example Input: [84.997, 58.227, -28.657]
Example Output:
38.189