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: [51.372, 141.276, 8.131, 168.539, 151.323]
Example Output: 104.128

Example Input: [138.63, 106.759, 86.625]
Example Output: 110.671

Example Input: [38.712, -36.822, -21.095, 62.066, 138.209, 122.548]
Example Output:
50.603

